style(Gruntfile): change indention

Change indention from 4 spaces into 2 spaces.
feat(GruntFile): add concated and uglified version

This commit adds grunt-contrib-concat and grunt-contrib-uglify grunt tasks. It is now possible to build an uglified version using `grunt build`.

BREAKING CHANGE: src/adaptive-scroll.js is now renamed into src/angular-adaptive-scroll.js