Suggestions for faster vision processing

[engunneer]

• [x] do we need the cv2.imwrite line in the loop? Perhaps put a conditional before it, so you can turn it on with a command line switch.
• [x] See if you can separate the image capture into a separate thread, such as http://www.pyimagesearch.com/2015/12/28/increasing-raspberry-pi-fps-with-python-and-opencv/
• [x] At a minimum, please see what our framerate is with the current method.
• [x] I'd add count to the NetworkTables as a new variable "heartbeat". The RoboRio can use this to know the camera is alive and functioning.

[simon-andrews]

• For now the image writing has been something that I would just comment in/out. I'll make a proper command-line argument for it tonight or tomorrow.
• Will look at threads after bag day. Seems like a lot of changes to the code, and I don't want to make large changes right now.
• Will add something for tracking framerate, probably tonight.
• Mathias and I will work on the heartbeat tonight. My side should be pretty easy so I will probably have time to work on something else after.

[simon-andrews]

Heartbeat is done. Having some trouble committing, but it's on the Raspberry Pi.