Move company logo from a background image to an img src [PD-526]

Moves company logos to img src rather than being CSS background images. After discussion on Jira with @haliscooper, we determined that this is a good enough improvement over what we had previously. Some users saw every image as broken. There will be more people seeing broken images now, but there should hopefully be fewer overall. Fixing what broken images remain is left for a later point in time.

All tests pass.

![2014-10-07-091614_726x502_scrot](https://cloud.githubusercontent.com/assets/3379265/4542670/55aa8f90-4e24-11e4-82a9-17fb56816c1f.png)