Create test for diff_drive_controller motion limits

[joshnewans]

Issue #242 revealed a bug with the diff_drive_controller's velocity/acceleration/jerk limit code.

Although a PR has been made to fix this, a test should be created to prevent this in future.

[roncapat]

I may contribute to this since I'm working on other tests. Any preferences on the behaviour to test? I mean, a sequence of steps and checks, a numeric input/ expected output example. Otherwise I will try to define a good test on my own in the following weeks :)