State more explicitly that concurrent requests are not supported

docs/en/modules/http.md

@@ -3,33 +3,34 @@
 | :----- | :-------------------- | :---------- | :------ |
 | 2016-01-15 | [esphttpclient](https://github.com/Caerbannog/esphttpclient) / [Vowstar](https://github.com/vowstar) | [Vowstar](https://github.com/vowstar) | [http.c](../../../app/modules/http.c)|
 
-Basic HTTP *client* module.
+Basic HTTP *client* module that provides an interface to do GET/POST/PUT/DELETE over HTTP(S), as well as customized requests. Due to the memory constraints on ESP8266, the supported page/body size is limited by available memory. Attempting to receive pages larger than this will fail. If larger page/body sizes are necessary, consider using [`net.createConnection()`](#netcreateconnection) and stream in the data.
 
-Provides an interface to do basic GET/POST/PUT/DELETE over HTTP(S), as well as customized requests. Due to the memory constraints on ESP8266, the supported page/body size is limited by available memory. Attempting to receive pages larger than this will fail. If larger page/body sizes are necessary, consider using [`net.createConnection()`](#netcreateconnection) and stream in the data.
+!!! note "Note:"
+
+    It is **not** possible to execute concurrent HTTP requests using this module. Starting a new request before the previous has completed will result in undefined behavior.
 
 Each request method takes a callback which is invoked when the response has been received from the server. The first argument is the status code, which is either a regular HTTP status code, or -1 to denote a DNS, connection or out-of-memory failure, or a timeout (currently at 10 seconds).
 
 For each operation it is also possible to include custom headers. Note that following headers *can not* be overridden however:
-  - Host
+
-  - Connection
+- Host
-  - User-Agent
+- Connection
+- User-Agent
 
 The `Host` header is taken from the URL itself, the `Connection` is always set to `close`, and the `User-Agent` is `ESP8266`.
 
-Note that it is not possible to execute concurrent HTTP requests using this module. Starting a new request before the previous has completed will result in undefined behavior.
-
 ## http.delete()
 
-Executes a HTTP DELETE request.
+Executes a HTTP DELETE request. Note that concurrent requests are not supported.
 
 #### Syntax
 `http.delete(url, headers, body, callback)`
 
 #### Parameters
-  - `url` The URL to fetch, including the `http://` or `https://` prefix
+- `url` The URL to fetch, including the `http://` or `https://` prefix
-  - `headers` Optional additional headers to append, *including \r\n*; may be `nil`
+- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
-  - `body` The body to post; must already be encoded in the appropriate format, but may be empty
+- `body` The body to post; must already be encoded in the appropriate format, but may be empty
-  - `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
+- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
 
 #### Returns
 `nil`
@@ -50,15 +51,15 @@ http.delete('http://httpbin.org/delete',
 
 ## http.get()
 
-Executes a HTTP GET request.
+Executes a HTTP GET request. Note that concurrent requests are not supported.
 
 #### Syntax
 `http.get(url, headers, callback)`
 
 #### Parameters
-  - `url` The URL to fetch, including the `http://` or `https://` prefix
+- `url` The URL to fetch, including the `http://` or `https://` prefix
-  - `headers` Optional additional headers to append, *including \r\n*; may be `nil`
+- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
-  - `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
+- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
 
 #### Returns
 `nil`
@@ -76,16 +77,16 @@ http.get("http://httpbin.org/ip", nil, function(code, data)
 
 ## http.post()
 
-Executes a HTTP POST request.
+Executes a HTTP POST request. Note that concurrent requests are not supported.
 
 #### Syntax
 `http.post(url, headers, body, callback)`
 
 #### Parameters
-  - `url` The URL to fetch, including the `http://` or `https://` prefix
+- `url` The URL to fetch, including the `http://` or `https://` prefix
-  - `headers` Optional additional headers to append, *including \r\n*; may be `nil`
+- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
-  - `body` The body to post; must already be encoded in the appropriate format, but may be empty
+- `body` The body to post; must already be encoded in the appropriate format, but may be empty
-  - `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
+- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
 
 #### Returns
 `nil`
@@ -106,16 +107,16 @@ http.post('http://httpbin.org/post',
 
 ## http.put()
 
-Executes a HTTP PUT request.
+Executes a HTTP PUT request. Note that concurrent requests are not supported.
 
 #### Syntax
 `http.put(url, headers, body, callback)`
 
 #### Parameters
-  - `url` The URL to fetch, including the `http://` or `https://` prefix
+- `url` The URL to fetch, including the `http://` or `https://` prefix
-  - `headers` Optional additional headers to append, *including \r\n*; may be `nil`
+- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
-  - `body` The body to post; must already be encoded in the appropriate format, but may be empty
+- `body` The body to post; must already be encoded in the appropriate format, but may be empty
-  - `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
+- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
 
 #### Returns
 `nil`
@@ -136,17 +137,17 @@ http.put('http://httpbin.org/put',
 
 ## http.request()
 
-Execute a custom HTTP request for any HTTP method.
+Execute a custom HTTP request for any HTTP method. Note that concurrent requests are not supported.
 
 #### Syntax
 `http.request(url, method, headers, body, callback)`
 
 #### Parameters
-  - `url` The URL to fetch, including the `http://` or `https://` prefix
+- `url` The URL to fetch, including the `http://` or `https://` prefix
-  - `method` The HTTP method to use, e.g. "GET", "HEAD", "OPTIONS" etc
+- `method` The HTTP method to use, e.g. "GET", "HEAD", "OPTIONS" etc
-  - `headers` Optional additional headers to append, *including \r\n*; may be `nil`
+- `headers` Optional additional headers to append, *including \r\n*; may be `nil`
-  - `body` The body to post; must already be encoded in the appropriate format, but may be empty
+- `body` The body to post; must already be encoded in the appropriate format, but may be empty
-  - `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
+- `callback` The callback function to be invoked when the response has been received; it is invoked with the arguments `status_code` and `body`
 
 #### Returns
 `nil`