Refactor Crafty.storage to use Pouch.js

Thanks for the tip.

Changed the PR to develop. 

Here's a link to the repo regarding the library I'm using https://github.com/daleharvey/pouchdb.

Basically the guys over at PouchDB are hard at work making it work across browsers and platforms and still pretty lightweight by itself.

I'm trying to write a demo that demonstrates the syncing capabilities of PouchDB syncing from a CouchDB database. That should allow game states to be saved to the local storage while the browser is offline and do the sync with external databases when it gets a connection.