Updating logo, removing unused assets

New logo per #242!

The typeface is a little less chubby, and the Open 'o' matches the rest of the letter widths more closely.

*What do you mean you can't tell the difference?*
![really](https://cloud.githubusercontent.com/assets/220240/4876073/83569980-62b4-11e4-857d-42c86ad7433a.gif)