Make jQuery dependence explicit, or remove this dependence.

[lewisje]

As I looked through the code, it appeared to rely on methods like $.extend and on jQuery-wrapped objects, and yet neither the README nor the config files mention that sketchpad requires jQuery; as much as I'd like to see a version of this package with the jQuery dependence removed, at least tell the users that they'll need it.

[jeanlucaslima]

@lewisje thank you, that is a really important point, I'll work on removing jQuery in this case.