untested changes to use opegm's vectorized api, and reserve space
untested changes to use opegm's vectorized api, and reserve space

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