Layers and functionalities integrated
 - Main activity now extends ExpandableListActivity 
 - OnCreate method updated to communicates the web service layer and
asks for data
 - Response handlers created. These inner objects realize defined
interface.
 - Synchronization method created. This method waits for both data and
presents it on the screen by utilizing previously created adapter.
 - Manifest updated to request persmison to connect to the Internet
 - Exercise 03 finalized