adding optional device id to getMemoryUsage
adding optional device id to getMemoryUsage

torch/cutorch,luketwitter/cutorch,Schakirov/cutorch_my,LinusU/cutorch,torch/cutorch,Schakirov/cutorch_my,Moodstocks/cutorch,adamlerer/cutorch,hughperkins/cutorch,hughperkins/cutorch,0wu/cutorch,Moodstocks/cutorch,torch/cutorch,wickedfoo/cutorch,LinusU/cutorch,Zhen-hao/cutorch,luketwitter/cutorch,clementfarabet/cutorch,yvan-sraka/cutorch,yvan-sraka/cutorch,adamlerer/cutorch,Zhen-hao/cutorch,clementfarabet/cutorch,0wu/cutorch,wickedfoo/cutorch