Update MonophylySimple_Clean.R

Corrected mistake:
- now number of taxa in a genus are compared to number of descendant tips of MRCA instead of number of descendant tips & nodes

Changes:
- output is now data frame instead of matrix
- larger phylogeny as test file

Additional output:
- number of genera causing focal genus to be non-monophyletic
- names of those genera (if less than 5)