A first version of a cookie based storage engine addition

[laviavigdor]

code review is required. also note that jquery-cookie is needed.

[guillaumepotier]

As promised, here a first glance and comments at your PR.

Also, to be merged, after updating your PR accordingly to my comments, you'll need to:

• [ ] fix test suite
• [ ] build minified version
• [ ] update README and index.html documentation

Thanks!