Simple Stack 0.1.0

Simple Stack 0.1.0 (2017-01-13)

• Added initial Backstack, StateChange and StateChanger classes.
• Backstack allows manipulation of state via goTo(), goBack() and setHistory().
• Demo persists backstack history through config change and process death.

Limitations:

• ViewState is not persisted
• scheduling state changes (starting a state change while another is in progress) is not allowed
• there is a possibility that state change can occur even after onPause()
• key and backstack are manually set to the custom viewgroup, which means these are not directly accessible in their child views (and the interfaces are ugly anyways)