[TASK] Update towards Twitter Bootstrap 3.0

Update markup and configuration to make extension compatible
with Twitter Bootstrap 3.0. Notice, the new markup is not
compatible anymore with branch 2.0 of TB.

More information regarding migration:
http://getbootstrap.com/getting-started/#migration
Merge pull request #58 from fudriot/feature-twitter-bootstrap-30

[TASK] Update towards Twitter Bootstrap 3.0