Batch sum dimension fix for CPU backend
Batch sum dimension fix for CPU backend

Jokeren/neon,dongjoon-hyun/neon,DougFirErickson/neon,dongjoon-hyun/neon,Jokeren/neon,NervanaSystems/neon,Jokeren/neon,DougFirErickson/neon,Jokeren/neon,DougFirErickson/neon,coufon/neon-distributed,NervanaSystems/neon,NervanaSystems/neon,NervanaSystems/neon,dongjoon-hyun/neon,coufon/neon-distributed,coufon/neon-distributed