Decreases CodeMirror's font size

From 16pt to 14px

Before:
![source 2014-03-16 00-16-42 2014-03-16 00-16-45](https://f.cloud.github.com/assets/1131196/2430188/c8ffb1a0-acc1-11e3-8b88-e50b1cfa6feb.jpg)

After:
![index html source 2014-03-16 00-15-23 2014-03-16 00-15-26](https://f.cloud.github.com/assets/1131196/2430182/9a3b953c-acc1-11e3-9ae0-73cf22c54137.jpg)