make a dictionary of tokens during initialization of LDAResults, use during predict() for 5x speedup
renamed 'cmd' module to 'cmdutils' to avoid module name conflict with native python 'cmd'.
The conflict was preventing yum from working on EC2
changed LDAResults.tokens to _tokens and added _tokenset to LDAResults.  Using properties and setters to bind changes in tokens to tokenset.
simplified API: changed _tokenset to tokenset and removed xtra tokenset method
keeping _tokenset, removing tokenset method
Merge pull request #33 from zigeuner/master

LDAResults.predict speedup and cmd module rename