Speed button know behaves like the volume button when tabbing forward or backward.
Added focus tracking to play/pause button. This fixes a bug where the tabbing, in certain condition, would get stuck on speed button.
Added test to verify that there is a certain order in the controls -- tabbing on the speed control will malfunction if it is not the case.
Merge pull request #854 from edx/jmclaus/bugfix_tabbing_video_speed_control

Speed button know behaves like the volume button when tabbing forward or...