More feature-complete demo application.

[mahonnaise]

Rules can be enabled and disabled individually. The rule-set is saved when the lint button is pressed and restored on startup.

The primary purpose is to aid development of new rules. Creating new rules is easier if you can use Chrome's or Firebug's debugger.

Fixes #150 (while it's not the web UI, it provides the same functionality) Fixes #273

[mahonnaise]

Since this is a somewhat heavy commit, I feel inclined to add this statement:

I wrote this for myself. I wanted a better demo/test application for testing purposes. It's fine to reject it.

[nzakas]

Yeah, the demo is really something I just used myself as I was debugging things, didn't really intend for it to be used by anybody else. I'll take a look at this when I have some time.