Merge pull request #120 from javieryanez/patch-2

Add README.md for DHT22 module by javieryanez

lua_modules/dht22/README.md

@@ -0,0 +1,22 @@
+# DHT22 module
+
+## Example  
+```lua
+PIN = 4 --  data pin, GPIO2
+
+dht22 = require("dht22")
+dht22.read(PIN)
+t = dht22.getTemperature()
+h = dht22.getHumidity()
+
+-- temperature in degrees Celsius  and Farenheit
+print("Temperature: "..(t/10).."."..(t%10).." deg C")
+print("Temperature: "..(9 * t / 50 + 32).."."..(9 * t / 5 % 10).." deg F")
+
+-- humidity
+print("Humidity: "..(h/10).."."..(h%10).."%")
+
+-- release module
+dht22 = nil
+package.loaded["dht22"]=nil
+```