Added support for Grunt

Use UglifyJS to compress CodeMirror scripts
Lint JavaScript with JSHint
Added imagemin Grunt task
Use Compass for CSS

Organized assets into subdirectories
Added Grunt Compass task
Use the box shadow mixin
Added Grunt watch task
Update table-mp6.css
Merge pull request #9 from bungeshea/feature/grunt

Add support for Grunt and Compass