Fix for SDK 1.8.x / V8 Android

This example project no longer works with SDK  1.8.x / V8 on Android, because changes in CommonJS modules aren't exposed beyond the module.  Thus, the changes to Date.prototype aren't visible outside of ````date.js````.

To fix this, we simply need to use the ````exports```` object in ````date.js```` and refer to this export whenever we need DateJS functionality.