Consider p value calculation for IC based sim calculations

[kshefchek]

When presenting results I'm often asked for a p value to determine if a match is significant. @drseb has proposed a way to generate p values for similarity scores here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2756558/. Would it be feasible and useful to add this to the phenodigm algorithm? Could we also add phenomizer as a matcher?