Fix pytorch1.5 compile error (#2524)

* replace AT_CHECK with TORCH_CHECK to support pytorch1.5

* fix compile warning, delete grid sample op

* fix ci pytorch version

* delete python3.5

* update version of pytorch and torchvision in ci

* change is_cuda to device().is_cuda()

* specify TORCH_CUDA_ARCH_LIST=6.0,7.0

* fix typo

* delete affine grid

* fix typos

* fix setup.py

* remove redundant comment