RF: removed all the clip_number references.  The user must prune their stimulus and functional data prior to the Model,Fit
RF: moved common features from each Model/Fit to the utilities
RF: made small fixes to the typedefs in cython function
TEST: got the tests working nosetest.  test_strf.test_brute_force_search is still failing with a segmentation fault.  it does not fail when run in IPython environment. commented out for now
RF: removed use of clip_number here too
TEST: removed use of clip_number