Allow permalinking to lines

Allows you to click on lines and grab a hash based permalink to it in your url bar, much like in github.

### Demonstration: http://paste.md-5.net/ruvudidote.html#L43

There is one hack in here I'm not real proud of: https://github.com/ammaraskar/haste-server/pull/new/seejohnrun:master...master#L3R21 but I can't really figure out a nice way to work around that properly. Basically when you change the hash, it calls the pop event because the history changes. Feel free to offer any better solutions to the problem if you have any.