Change License to GNU GPL3

Hey folks,
We had a request to change this license from Creative Commons over to GNU GPL3. I wanted to propose it and make sure everyone is ok with it before I make the change.

http://www.gnu.org/licenses/gpl-3.0.txt

Please sound off!

[imtal]

I commented this at the BrickPi_Python repository as well: as much of your software has the form of a library, I would expect LGPL which is copyleft towards the library itself but offers somewhat more freedom in its use.