Vectorize ElementWiseDivide using Eigen
Vectorize ElementWiseDivide using Eigen

Summary: Replace for loop with Eigen operations in method ElementWiseDivide

Reviewed By: Yangqing

Differential Revision: D4602516

fbshipit-source-id: 6b19de8190d5e29ffe52359d0cd0c27cf03c52e2

xzturn/caffe2,sf-wind/caffe2,davinwang/caffe2,sf-wind/caffe2,xzturn/caffe2,pietern/caffe2,pietern/caffe2,sf-wind/caffe2,Yangqing/caffe2,pietern/caffe2,davinwang/caffe2,davinwang/caffe2,pietern/caffe2,Yangqing/caffe2,xzturn/caffe2,Yangqing/caffe2,xzturn/caffe2,bwasti/caffe2,caffe2/caffe2,davinwang/caffe2,bwasti/caffe2,xzturn/caffe2,bwasti/caffe2,Yangqing/caffe2,sf-wind/caffe2,Yangqing/caffe2,davinwang/caffe2,sf-wind/caffe2,bwasti/caffe2,bwasti/caffe2,pietern/caffe2