General maintenance.

Changes:
*got rid of a bunch of old code
*got rid of printing to files in neuralAssociativeMemory.py since there
 are no files there.
*fixed get_key_from_vector threshold in associativeMemoryTester.py
*got rid of the non-gpu funcitonality --- basically has to be run on
 gpu's now
*number of gpu's fixed at 4. if there are fewer, the c library is
 capable of detecting that and adjusting accordingly.