Merge pull request #1 from khughitt/master

Added pre-reqs and vignette example to README
Added code for filtering low expression genes
Changed lib.size parameter from colSums(counts) to NULL. (log2CPM fct)
removed combat estimates from combatMod output
Fixed an issue preventing vignettes from building
Added pasilla to deps in order to build vignettes (done when installing with devtools)