Changed main toolbar to be flush with the rest of the window. 

Tested on OS X, Linux, and Windows, but could probably use more testing.

Before, after (respectively):

![OS X](http://i.imgur.com/NK72QIQ.png)

![Linux Mint](http://i.imgur.com/zaDjU03.png)

![Windows 8](http://i.imgur.com/4sVruBK.png)