ENH: removed the signal normalization from popeye.gaussian and added a 5th scaling parameter beta
ENH: added a normalization function for specifying the ranges an array occupies
TEST: added tests for normalization and modified gaussian tests to reflect the addition of the new scaling parameter
RF: added a normalizing factor to the hrf
RF: made it so that multiple shared memory arrays can be used with visual stimulus
RF: modified the stimulus class so that it can represent multiple shared memory sessions
ENH: my first stab at adopting the k-fold cross-validation from dipy
RF: fixed it so that the xval takes model instead of stimulus (which contains the stimulus)
RF: modified calls inside gaussian
ENH: added cross_validation for importing
RF: fixed up the xval
RF: turned off the debug mode
RF: changed the cross_validation to be run-based rather than sample-based.  This is necessary for any time-series where temporal order must be preserved.
TST: added tests for the cross validation.