Add params to codemirror 

so that the user can select a font, size, and line-height.

It's for this:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_id=8549&tracker_item_id=28807

But, as a bonus, it also solves this:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=29467