Improve copy and the campaign page to have more explicit calls to action

These changes improve the campaign page (which is now linked to as "Donate Now!" from the menu) to have a bit more explicit copy writing and a more immediate calls to donate money. It also puts a more explicit deadline onto the page. It currently 

![](http://s3itch.paperplanes.de/Campaign__Rails_Girls_Summer_of_Code_20130529_183816.jpg)