add docs to spatial_pooler.py
add docs to spatial_pooler.py

marionleborgne/nupic,ywcui1990/nupic,badlogicmanpreet/nupic,badlogicmanpreet/nupic,arhik/nupic,rhyolight/nupic,vitaly-krugl/nupic,arhik/nupic,subutai/nupic,scottpurdy/nupic,neuroidss/nupic,alfonsokim/nupic,rcrowder/nupic,lscheinkman/nupic,rcrowder/nupic,scottpurdy/nupic,pulinagrawal/nupic,ywcui1990/nupic,lscheinkman/nupic,pulinagrawal/nupic,vitaly-krugl/nupic,alfonsokim/nupic,rcrowder/nupic,scottpurdy/nupic,alfonsokim/nupic,pulinagrawal/nupic,marionleborgne/nupic,numenta/nupic,rhyolight/nupic,badlogicmanpreet/nupic,EricSB/nupic,ywcui1990/nupic,subutai/nupic,lscheinkman/nupic,vitaly-krugl/nupic,EricSB/nupic,neuroidss/nupic,EricSB/nupic,arhik/nupic,rhyolight/nupic,neuroidss/nupic,marionleborgne/nupic,numenta/nupic,numenta/nupic,subutai/nupic