Optimise data-uri PNGs 

I decoded the base64 and exported it into a png file, then I ran ImageOptim on it and re-encoded it to base64.

For example, in the case of the d2 pick icon:
Before: 3774 bytes
After: 564 bytes
Weight loss: 85.1%

![screen shot 2014-06-30 at 10 35 06](https://cloud.githubusercontent.com/assets/85783/3427947/f114c010-0039-11e4-93b6-9346803ebc9b.PNG)

![ ](http://media.giphy.com/media/qOZ3XVz9C35mM/giphy.gif)