added css concat and cssmin to build prozess
so far we only create the minified css file. I do not really know how to add it later J
Merge branch 'master' into feature/build-css

Conflicts:
	Gruntfile.js
	package.json
readded config to Gruntfile, vanished during merge
Merge pull request #22 from glaubinix/feature/build-css

Feature/build css