Grunt builds, LESS styles; related to #66 and #77

- [ ] **Delete branch after merging**

Changes:
- grunt.js is now used. It automatically compiles LESS to CSS and creates minified versions of our CSS and JS files.
    - For example, `excelsior.less` will generated `excelsior.css` and `excelsior.min.css`
- All styles have been converted to LESS. All of Foundation's SCSS files were removed.
- This pull request also includes the modules for LESS, Uglify, and JSHint. Since we'll all be using the same modules, we will all produce the same output regardless of platform.

Grunt usage:
- install [node.js](http://nodejs.org/)
- run Node and install grunt with `npm install -g grunt-cli` ([more detailed instructions here](http://gruntjs.com/getting-started))
    - if you're in Windows, make sure to launch node &mdash; you should have a different command line prompt while it's running, probably a single `>` bracket. Don't use Cygwin!
- type `grunt less` to compile LESS or `grunt uglify` to minify JS

LESS usage:
- Just write plain old CSS (or [LESS](http://lesscss.org), it's very simple!) in the appropriate `*.less` file and use grunt to compile it as explained above