Gitignore Bower update.

Excluded `lib/` folder from the project.
Added `bower_components/` folder to `.gitignore`.
Major build update.

Excluded `lib/` folder from the repo index.
Removed previously added `csscomb` module and tasks.
Added Bower support. Bower automatically  will run after the `npm
install` task.
Added `grunt update` task, that will copy bower components into the
`lib/` folder;
Updated existed grunt tasks.