Replace compass dependency + cleanup

- replace dependency on compass with node-sass. this allows all development dependencies to be installed via npm
- remove old folders from `bower.json`
- remove `coffee/test_data.coffee`
- fix README instructions
You probably want to have it be `'node_modules/node-sass/bin/node-sass --output-style...'` here, since people who just run `npm install` might not have the module in their path.