Modified to enforce framerate control at the application level in addition to at the driver level.  This is necessary since the drivers for my webcam did not obey the requested framerate.
Merge pull request #16 from liangfok/feature/app_level_framerate_control

Modified to enforce framerate control at the application level in additi...
Uses ros::Rate to enforce software framerate instead of custom time check
changelog updated
0.1.9