Merge pull request #6 from francois-keith/master

Add gripper frames and correct the initialization of the hand frames
Remove the None members from the definition of a humanoid robot.

These members still need to be redefined when describing a humanoid robot
Merge pull request #8 from mehdi-benallegue/master

Remove the None members from the definition of a humanoid robot.
Correct computations of the X component of the ZMP

Correct also the linear force part of the Y component of the ZMP.
Fully support the case of non planar feet case in ZMP from forces.

The added terms should be negligible in most cases, even when feet are not planar, but this version is more general.
[Travis] Use travis submodule.
Leave the debian folder to the debian branch.
Only annoy me.
[Win32] Correct macro.
Remove useless ARGET_LINK_LIBRARIES.