Using two new utils:
1. `createNavigationPropConstructor`, which is now preferred over `createReduxBoundAddListener`.
2. `initializeListeners`, which is necessary to trigger the event listeners with the initial state.
* Update Stacks{In,Over}Tabs example for better clarity
* Remove redundant navigationOptions in stack examples
* Update text in ReduxExample to clarify which route is being used
* [ReduxExample] Programmatically generate initial state
* [ReduxExample] Return original state if nextState is null
* [Docs] Add getStateForAction to redux integration example
* [Docs] Add link to ReduxExample app
* [Docs] Give each example a 'DRY' README linking to real docs
* [Docs] Clean up the Contributors guide a bit
* [Docs] Remove numbers from sections in Contributors guide
They don't seem very meaningful, and don't need to be done in order
* [Example] Fix the ReduxExample app
Just a bit of cleanup so it can run.
* [Example] Remove AsyncStorage persistence from ReduxExample
It's a cool feature, but isn't necessary to demonstrate how to use
react-navigation and may cause more confusion than it's worth.
