Trying to play with the header image

I am not 100% happy with the header. It's way to dark.

Because of that I want to try out a few things in this PR till we find something better.

This is my first try:

![bildschirmfoto 2014-08-28 um 20 00 18](https://cloud.githubusercontent.com/assets/56195/4080267/36cf295c-2edd-11e4-89b6-e1a3603e7df7.png)

The color of the gray is not good yet, but having the logo in the header makes it recognizable. And I played with the font in the header. At first I tried to get a really 8-bit font, but they didn't look that good there.

What do you think? Is this the right direction? What would you change?