Restructure JS to be AMD-compatible

This pull request refactors the Javascript a bit to make it [AMD](https://github.com/amdjs/amdjs-api/wiki/AMD)-compatible. It also drops JS compression, because this is a debug toolbar, and there's no reason to compress assets that are only going to be used in debugging -- in fact, if someone discovered a problem with an interaction between the Django Debug Toolbar and their Javascript code, having compressed JS is only going to make it *harder* to debug. I also removed the `jQuery.noConflict(true)` call from toolbar.js in favor of only loading the jQuery library if it hasn't already been defined on the page, which should solve the same problem more neatly.

This diff contains a fair number of whitespace-only changes in toolbar.js; to ignore those changes when viewing the diff on Github, you can add `?w=1` to the URL. I find that makes pull requests like these easier to review.