Merge pull request #26 from qbuat/master

Add yields calculation in postfit.py + update yields-postfit accordingly
weighted mass plots
use symlink for BDTs
add jk_number to categories + first version (incomplete) of tree-jackknife
Add symmetrization threshold in histfactory + some dev in tree-jackknife
Update in tree-jackknife (no BDT score yet)
improve or of cuts
Add classifier/scores
No call of Classifier from tree-jacknife
remove useless comment
small fix