Adding compass support into meanjs generator

Hello, I added support to compass.

Just create a file.scss into the css folder, it will get compiled into file.css.

See the file /public/modules/core/css/core.scss  as an example.

I couldn't find any doc on how to run mocha test on the yeoman generator itself, I wrote the test, but didn't run it.

To install compass, usually run  

gem install compass.