Dynamic width #editorPane

Changed the positioning of elements to accommodate the #editorPane being rendered to different widths in different browsers without overlapping or gaps.

Before:
![image](https://cloud.githubusercontent.com/assets/4296045/3556992/7dbb63ea-092a-11e4-835a-7f3b373716aa.png)

After:
![image](https://cloud.githubusercontent.com/assets/4296045/3556997/877659bc-092a-11e4-91ea-277cfd88eaeb.png)