Simple modifications to allow for production and development asset manag...

Simple modifications to allow for production and development asset management.
- Added csslint with bootstrap's .csslintrc file (fixed css lint warnings in common.css)
- Added cssmin and uglify to compress assets during production builds
- Added assetmanager to switch asset files in the template respectively for production and development builds
- Centralized css and js files into a single assets.json file that can be used in both grunt and the app