Create fpkm_merge.py

fpkm_merge is a function that takes a file of fpkm tracking files from single cell RNA seq runs and outputs two files: one with all of the fpkm values for each cell/condition/timepoint and one with info for each cell.  These files can then be used with monocle (http://monocle-bio.sourceforge.net/) or Singular (http://www.fluidigm.com/singular-analysis-toolset.html) to do analysis (PCA, clustering, etc.)