Added yaml-cpp and its toolfile.

See also http://twiki.cern.ch/twiki/bin/view/CMS/OfflineComputingPlanningMeeting20140107.
Merge pull request #313 from degano/IB/CMSSW_7_0_X/stable

Add yaml-cpp.
Merge remote branch 'origin/IB/CMSSW_7_0_X/stable' into IB/CMSSW_7_0_X/stable