Fixed UI bugs in code block editor

This submission fixes the following issues in the new code block editor:
1. Changed editor font to 'Consolas' - This fixed the issue with the quirky selection highlight below:
![image](https://cloud.githubusercontent.com/assets/5710686/4247513/d3c77cf4-3a5a-11e4-8c5e-ba292433b766.png)
2. Select the text in code block, click outside to commit, blue selection stays.
3. Clicking on the area shown doesn’t make the code block into editing mode - This was because this area was occupied by the vertical scrollbar, which has been disabled
 ![image](https://cloud.githubusercontent.com/assets/5710686/4247534/1fdef55e-3a5b-11e4-9d70-dfc2f0b98904.png)

and ofcourse we now have fixed width point as mentioned in point (1) :)

@Benglin PTAL