Improve ace integration

Integration with the ACE code editor is a little wonky right now. These changes fix the line numbering and editor height.

**Before:**

![misoproject com-code-block-before](https://cloud.githubusercontent.com/assets/677252/3163382/14947fa4-eb3f-11e3-850d-fe411e67d732.png)

**After:**

![misoproject com-code-block-after](https://cloud.githubusercontent.com/assets/677252/3163384/199233ca-eb3f-11e3-90bc-8686b3599ee5.png)

@iros I've only been able to do limited testing because of bizarre StaticMatic behavior. Could you test this for me?