Made JS scripts load asynchronously

Made all the `javascript_include_tag` tags have `:async => true` so that the scripts are loaded and run asynchronously. This prevents it from blocking DOM construction and from blocking execution before the CSSOM is done its thing. The scripts should run fine despite them potentially loading out of order, since most things rely on waiting for the document to finish anyway (with jQuery's `jQuery(document).ready(...)` or Prototype's `document.observe('dom:loaded', ...)`).

There's a bit of code formatting cleanup here and there too.

EDIT: Seems that some things can't be loaded asynchronously, so I'll have to go through them carefully.