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 assets files in the template respectively for production and development builds
Update assetmanager to 0.1.1

assetmanager 0.1.1 supports external asset files i.e. cdn assets.
Merge branch 'master' of https://github.com/ReedD/mean into ReedD-master

Conflicts:
	package.json
Merged right
missing grunt-contrib-csslint