added PIL to watch world

Conflicts:

	log/correlation.eps
	log/hierarchy.eps
fixed grouper bug that ate memory when forming higher level features
Cleaned up in preparation for 0.4.0 release
Added .bib file
Added users guide pdf
Added log directory and README
adjusted constants in image_2D world
Added save methods for agent
Converted nearly all numpy 1D arrays to 2D arrays for consistency
Fixed bugs relating to 2D array conversion, dimensions, and indexing
Fixed a few more bugs realted to indexing and array sizing
A few debugs on the watch world
Performs visualizations only at the end of a world
group size naturally limited, rather than thresholded
fixed number of random features created at group creation
features migrate to positions based on the inputs Becca receives
users guide updated. Dynamic feature learning still under construction.
renamed grouper to perceiver
reworked fatigue and inhibition in features
cleaned out debugs and commented out sections