upgrade to herwigpp 2.7.1 and thepeg 1.9.2
Merge pull request #888 from mkirsano/toherwigpp271_1

upgrade to herwigpp 2.7.1 and thepeg 1.9.2
Merge remote branch 'origin/IB/CMSSW_7_1_X/stable' into IB/CMSSW_7_0_X/stable