fixed bug omitting muons from the lepton selection
implemented fix for possible vector out of range exceptions
Merge pull request #4485 from cms-btv-pog/JetFlavor-LeptonSelectionAndOutOfRangeFixes_from-CMSSW_7_1_1

Fix for jet flavor lepton selection and possible out of range exception: Backport from 7_2_X to 7_1_X