Fixed the Gruntfile to rely on compass installed with bundler

The contributing documentation asks about installing compass through
Bundler, so the Gruntfile should expect it as well.
Version bump to 1.2.0
trigger ready event only after full instansiation, as documented
fixed typo
Merge pull request #2098 from liorch88/ready-event-fix

Trigger ready event only after full instansiation (as documented)
Added support for optgroup classes inheritance
Made the group classes support look more like the option classes support
Merge pull request #2106 from liorch88/optgroup-class-support

Added support for optgroup classes inheritance