Added functionality

Hi Vishnu,

This is a great library, and I'd love to contribute some minor additions. Most easily, I added some additional getters in UIElement, since there's some additional goodies in the data Map depending on what DOM element is being inspected (i.e. input vs div). Also added some additional commands to AndroidBridge (sendTextEvent & sendKeyEvent), which are utilized by the newly added Keyboard class that simulates the physical keyboard on the device. This class helps out when Calabash's "set_text" functionality doesn't work properly. 

As always let me know if there are any questions.

Thanks,
Mike