#203 add unit tests for pickle dump/load of all data objects

[Nathan Oostendorp]

Some of the data objects in SimpleCV don't pickle clean -- we need make sure they do so they can be stored persistently.

Make sure Image/ImageSet/DrawingLayer/Feature/ColorMap/ColorCurve/Segmenters etc (Anything that holds data and would be lost on process exit and their subclasses) can be pickled, and add unit tests for each.