Merge pull request #52 from jjacob/master

Changes as detailed below
adding an example for RooFit, next one to follow
renamning examples/roofit.py
adding advanced RooFit example
adding expert RooFit example (what we need)
'adding' the holy grail of RooFit
a few fixes
adding RooFitFit to tool/Fitting.py and a unit test for it
nicer format
adding RooFitFit tests to travis build (please write more tests!)
adding Paras' RooFit code
adding gaussian constraints to RooFitFit (and tests, of course)
adding constraints to example. Also some code for later (profile LL)
saving the result of the fit for later access (i.e. covariance matrix)
adding fitter option
Merge pull request #54 from kreczko/merging

RooFit examples
Slightly modifying comments in 01_get_fit_results.py
Adding lines to enable use of central samples from a different folder in /storage/TopQuarkGroup/results/histogramfiles/.
(May not be needed long term.)
Correcting Data row heading in fit results tables.
Correcting correlation plots so QCD and signal are not swapped round.
Correcting to new luminosity in correlation plot titles.