Feature/easystar

As an attempt to contribute to Panda.js I've created a easystarjs plugin and also updated the Tiled plugin a bit so the two are easier to combine. Please, checkout the README.md in easystarjs to see how this would be implemented. 

Would love to hear comments / suggestions / thoughts.

Edit: I've also added comments to the tiled plugin. If this implementation would be acceptable, this would fix ekelokorpi/panda.js-plugins#7