Fix the ReduxExample app (#900)

* [Redux example] Use HTTPS-enabled endpoint to get npm modules

To fix 'yarn install'

* [Redux example] Add ReduxExample to rn-cli.config.js

This prevents those annoying @providesModule naming collisions

* [Examples] Add a basic README linking to the usage instructions

examples/README.md

@@ -0,0 +1,5 @@
+# Examples
+
+## Usage
+
+Please see the [Contributors Guide](https://github.com/react-community/react-navigation/blob/master/docs/guides/Contributors.md#development) for instructions on running these example apps.

rn-cli.config.js

@@ -14,6 +14,7 @@ const examples = [
   'NavigationPlayground',
   'HelloHybrid',
   'LinkingExample',
+  'ReduxExample',
   'Chat',
 ];