Minor shanges to other notebooks + cleanup.

Removed pad_value option from cSNMF.ipynb.

Replace cSNMF.py to change tail_cutoff to 0.4 and remove padding and default beta value to len(D.T)//2

Changed factorize to return error.  The error value was being lost and could not be recalculated.  Global problem?

Changed factorize to return error.  The error value was being lost and could not be recalculated.  Global problem?

Beta value changed from nanmean(D) to 100*nanmean(D).

Added axe_H function.