Added support for using SpaceNavigator 3d mouse for manual robot control

* Split Joystick class into Joystick, GamepadJoystick, SpaceNavJoystick
* Added spacenav dependencies to install scripts for ubuntu and arch
* Joysticks now return normailzed [-1,0] values and Processor handles damping
* Joysticks now use world coordinates for visible robots and body coords as fallback
* Added info to soccer docs page about SpaceNavigator
* note: to use SpaceNavigator, you must have spacenavd userspace driver daemon running
removed debug printing
added spacenav dependencies to travis
Merge pull request #168 from RoboJackets/3dmouse

Added support for using SpaceNavigator 3d mouse for manual robot control