enh make constraint pruning in 1-slack ssvm slightly more intiutive
enh make constraint pruning in 1-slack ssvm slightly more intiutive

massmutual/pystruct,amueller/pystruct,d-mittal/pystruct,d-mittal/pystruct,pystruct/pystruct,pystruct/pystruct,wattlebird/pystruct,massmutual/pystruct,amueller/pystruct,wattlebird/pystruct