Use chrono library instead of sys/time.h to get the the time from epoc
Use chrono library instead of sys/time.h to get the the time from epoc

Summary: Remove the dependency on sys/time.h, and use c++11 feature chrono library, which is more portable.

Reviewed By: Yangqing

Differential Revision: D4486569

fbshipit-source-id: 86be58c6e9bc410e726a4799bc4d2be86fdd1dd4

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