documentation update

Author: Stefan Kuper

README.md

@@ -1,2 +1,47 @@
 # ArduinoFritzApi
 An arduino Library for Automation of Fritz!Box, Fritz!DECT and FRITZ!Powerline devices
+
+# Implemented Functions
+
+Following functions have been implemented:
+
+<dl>
+  <dt>setSwitchOn</dt>
+  <dd>Switch actor on, return new switch state (true=on, false=off)</dd>
+  <dt>setSwitchOff</dt>
+  <dd>Switch actor off, return new switch state (true=on, false=off)</dd>
+  <dt>setSwitchToggle</dt>
+  <dd>Toggle switch state, return new switch state (true=on, false=off)</dd>
+  <dt>getSwitchState</dt>
+  <dd>Retrieve current switch state (true=on, false=off)</dd>
+  <dt>getSwitchPresent</dt>
+  <dd>Check for presence of a switch with the given ain (true=present, false=offline)</dd>
+  <dt>getSwitchPower</dt>
+  <dd>Get current power consumption in Watt</dd>
+  <dt>getSwitchEnergy</dt>
+  <dd>Get total energy since last reset in Wh</dd>
+  <dt>getTemperature</dt>
+  <dd>Get temperature in °C</dd>
+
+# Error handling
+
+In case something went wrong one of following error codes will be thrown:
+
+```
+   FRITZ_ERR_HTTP_COMMUNICATION  -1001
+   FRITZ_ERR_NO_CHALLENGE        -1002
+   FRITZ_ERR_NO_SID              -1003
+   FRITZ_ERR_EMPTY_SID           -1004
+   FRITZ_ERR_INVALID_SID         -1005
+   FRITZ_ERR_VALUE_NOT_AVAILABLE -1006
+```
+
+In Addition one of the following HTTP STATUS Codes may be thrown:
+
+```
+   Bad Request                    400 
+   Forbidden                      403
+   Internal Server Error          500
+```
+
+