Replace mark-active with (use-region-p)
Changes to come closer to Emmet support, to allow for better consistency of behavior.

Major changes include:

  * Parser is changed to use Emmet's bracket syntax for properties
  * now uses point as the right bound of the expression
  * searches for left bound from right bound. This is poorly executed as of now
Uses backward-char and less selective stop-words.  Seems to basically work in all cases I have managed to test.
Merge pull request #30 from pobocks/issue_28

Issue 28 - This seems to work better and fail on less cases than the current code, anyway.  I've seen some pausing when expanding hiccup inside Clojure code, but the existing code fails entirely in the same spot, so it's an improvement.