Abstract Syntax Tree View

This adds a new view for Abstract Syntax Tree View. I've uploaded this branch to people.mozilla.org, so you can play with an instance [here](http://people.mozilla.org/~rfletcher/scanjs/client/)

Known 'bug', when viewing AST a user has to click the CodeMirror console before it renders/updates. I'm hoping @mozfreddyb will have an idea. :)

Details:
* delete prettify, since we don't use it
* cleaned up index.html, moved CSS to single app.css in client/css/ directory
* added new pane for AST View. 

Todo:
* fix bug referenced above
* add functionality to either print to AST to console (just uncomment a line) or write it to a file, possibly based on command line argument.
 * @mozfreddyb and @pauljt, what do you think? Just print it to a standard file all the time or make it a command line argument? I think printing to STDOUT is unnecessary/excessive.