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.
[Windows] Correct macro and export.

In windows, the deprecated flag should be placed before the
function declaration.
Also, correct macro name for dllimport.
Use boost::pi rather than M_PI for portability.
Only annoy me.