Add LiveScript support

Adds quite comprehensive LiveScript syntax support, much more so than the other open LiveScript PR (#222). I started working on mine before noticing that one, which is why this is its own pull request.

There are some things which I couldn't figure out how to cover fully (mostly named function syntax), but those highlight pretty well even without explicit support due to the keywords found within, so I'm personally okay with how they look as-is.

I haven't added a sample to `src/test.html` because I was wondering if you'd prefer the code to be more like "actual" code or can it just be random stuff that demonstrates as much language features possible? Because that's what my personal test file for this looks like at the moment.