Added a service

BootReceiver calls GogoService on boot
Code cleanup
Added a BroadcastReceiver for connectivity state, which would call the
service to start/stop gogoc depending on the current connectivity state

* Added stateChanged method to the service interface to check the
  connectivity state & accordingly start/stop gogoc
* Added override for onStartCommand method, which calls stateChanged.
Use .equals method for string comparison instead of ==