small fix for one of the examples (bar->hist)
added histogram preparation to hist_utilities
moved latex labels to config/
changed from TFile to rootpy.io.File
added new plotting function for data-MC comparison

- new CMS style variables
- added electron eta plot example for cross section analysis
- added mttbar plot example (incomplete, missing QCD from data) for Z' analysis
setting default MC error to 0
Merge pull request #27 from kreczko/master

New functions for histogram plotting