2.2/fix button icon

This has been killing me for a while. I finally decided to inspect. Removing the `vertical-align: middle;` corrects the position.

Before:

![screen shot 2014-12-04 at 10 48 22 am](https://cloud.githubusercontent.com/assets/1425304/5301074/954e4b62-7ba3-11e4-8dc7-5eace38d9747.png)

After:

![screen shot 2014-12-04 at 10 48 40 am](https://cloud.githubusercontent.com/assets/1425304/5301075/9564867a-7ba3-11e4-860a-017af968d921.png)