#91 Add a "sketch" interface

[Nathan Oostendorp]

Similar to Arduino and Processing, I would like to be able to include a module SimpleCV.Sketch which would give me some syntax for setting up a prototyping environment. I provide two methods -- start() which initializes any globals (camera, display, arduino, etc) and loop() which is the equivalent of the interior of the while True in most of our examples. It also should have implicit access to any globals (possibly thru use of an introspective decorator?)

Probably the way I invoke this is a line at the bottom of my script:

SimpleCV.Sketch(start, loop)