Remove all SCSS/SASS nonsense

The grunt file was just not processing the .scss files properly. Instead
of wasting time fiddling with this, I decided to just use straight CSS.

See #9.
Change the way images are handled

Bootstrap's icons need to be in a /img/ folder by default. Since I don't
want to touch the default CSS, I renamed the image folder instead.

See #9.
Prevent magnification of AngularJS

AngularJS relies on some naming conventions to do its dependency
injection. If we use minify, it wantonly renames stuff without caring
for those conventions causing all things to break. The solution is to
*not* minify for now.

For more information

https://groups.google.com/d/msg/yeoman-dev/642ocaWEHw8/Q2bN0UTw6sgJ
http://docs.angularjs.org/guide/dev_guide.services.injecting_controllers

See #9.
Add reverse proxy

To circumvent the same origin policy, I have created a simple reverse
proxy using node-http-proxy
(https://github.com/nodejitsu/node-http-proxy).

To initialize the entire system, be sure to call `npm install` followed
by `npm start`.

See #9.
Fix subtle bug with the factory for Submission

1) Ensure that the submission factory *must* be returned.
2) Fix typo for function name respondToChallenge().

See #9.
Make GET request to Coursera

This makes use of our reverse proxy to circumvent the same origin
policy for XMLHTTPRequest(). Code is in a bit of a mess since I don't
know of a good way to properly organize the callbacks.

See #9.