Align tensors with 64 bytes
MKL, and maybe other future used libraries (NNPack, MKLDNN, ..) can work faster on aligned data (usually 64 byte aligned, see reference), also would make possible to create a version of strided iterator with vectorized instructions on aligned data, so would be good to have newly created tensors already aligned by default. 

This could be done with a custom allocator or offseting tensor data on creation, maybe some restrictions could be done for small tensors to avoid excessive memory usage caused by aligning small tensors like a scalar tensor.

Reference:
https://software.intel.com/en-us/mkl-linux-developer-guide-coding-techniques
