Adjust the detail, fix program bug

lua_modules/dht_lib/README.md

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+# DHTxx module
+
+This module is compatible with DHT11, DHT21 and DHT22.  
+And is able to auto-select wheather you are using DHT11 or DHT2x
+
+No need to use a resistor to connect the pin data of DHT22 to ESP8266.
+
+##Integer Verison[When using DHT11, Float version is useless...]
+### Example  
+```lua
+PIN = 4 --  data pin, GPIO2
+
+DHT= require("dht_lib")
+
+DHT.read(PIN)
+
+t = DHT.getTemperature()
+h = DHT.getHumidity()
+
+if h == nil then
+  print("Error reading from DHTxx")
+else
+  -- temperature in degrees Celsius  and Farenheit
+
+  print("Temperature: "..((t-(t % 10)) / 10).."."..(t % 10).." deg C")
+
+  print("Temperature: "..(9 * t / 50 + 32).."."..(9 * t / 5 % 10).." deg F")
+  
+  -- humidity
+
+  print("Humidity: "..((h - (h % 10)) / 10).."."..(h % 10).."%")
+end
+
+-- release module
+DHT = nil
+package.loaded["dht_lib"]=nil
+```
+##Float Verison
+###Example
+```lua
+PIN = 4 --  data pin, GPIO2
+
+DHT= require("dht_lib")
+
+DHT.read(PIN)
+
+t = DHT.getTemperature()
+h = DHT.getHumidity()
+
+if h == nil then
+  print("Error reading from DHT11/22")
+else
+  -- temperature in degrees Celsius  and Farenheit
+  -- floating point and integer version:
+
+  print("Temperature: "..(t/10).." deg C")
+  print("Temperature: "..(9 * t / 50 + 32).." deg F")
+  
+  -- humidity
+  print("Humidity: "..(h/10).."%")
+end
+
+-- release module
+DHT = nil
+package.loaded["dht_lib"]=nil
+```
+## Functions
+
+###read
+read(pin)
+Read humidity and temperature from DHTxx(11,21,22...).
+**Parameters:**
+
+* pin - ESP8266 pin connect to data pin
+
+### getHumidity
+getHumidity()  
+Returns the humidity of the last reading.
+
+**Returns:**  
+* last humidity reading in per thousand
+
+### getTemperature
+getTemperature()  
+Returns the temperature of the last reading.
+
+**Returns:**  
+* last temperature reading in(dht22) 0.1ºC (dht11)1ºC
+*