Correct the time incrementation for control recomputation

This modification allows to avoid a strange stairs shape of the controller.
Merge pull request #28 from mehdi-benallegue/master

Correct the time incrementation for control recomputation
Change the GripperControl entity. Close #27.

The gripper control entity now prevents closing the gripper more
if the maximal torque value is reached.
[Travis] Use jrl-travis submodule.
No more debian in master branch.
Only annoy me.