Update to less-1.3.3 (works with bootstrap-2.3.0), add a test and improve logging

This pull request includes an update to less-1.3.3 and a test that checks compilation of bootstrap-2.2.2 and boostrap-2.3.0 among other changes.  The summary is:

* Upgrade to less 1.3.3
* Upgrade to Rhino 1.7R4
* Upgrade to grails 2.2.0
* Spock test for compilation of bootstrap
* Improved logging (log4j instead of println)