Add support for toggling multiple class names

ClassToggle now allows designers to specify multiple classes to toggle
on and off. The class names are not checked for existence first and are
simply toggled. For further details, see
http://abitgone.github.com/jQuery-Plugins/ClassToggle/#h-ex4.

This closes issue #7.
Merge pull request #8 from abitgone/feature/7/toggle-multiple-classnames

Add support for toggling multiple class names