Fixes for issue #92

Fixes for issue #92:
 - replaced pfRelativeIsolation(0.3) with pfRelativeIsolationRhoCorrected()
 - removed pfRelativeIsolation histograms from ElectronAnalyser
 - removed obsolete comments

TTbar+X analyser: 
 - removed obsolete comments
 - uncommented PFRelIso lepton analysers
 - removed non used variables

Other:
 - Added stand-alone instructions for older boost versions and added ROOT files to gitignore