Added Support for Typescript

As explained on [this Thread](http://www.html5gamedevs.com/topic/8387-phaser-isometric-plugin/page-4#entry56922) the approach of extending the behaviour of Phaser's core classes by adding methods and properties to them, makes the game incompatible with Typescript. That's because it's not possible in Typescript to merge class definitions. 

This pull request solves this problem by adding references that are not extending Phaser's core classes. More specifically
1. Added a property to `projector` where it was before accessed by `game.iso`
2. Added a method `addIsoSprite()` where it was before accessed by `game.add.isoSprite`

The other important addition is the inclusion of `phaser.plugin.isometric.d.ts` file with Typescript Definitions. It's still not complete, but should be enough to run the examples on the website.