Useful cuda codes with annotations inside .

I've heavily commented the code about RoIAlign for better usage . Two different version are included , and no much different effect founded between them.

(Not checked yet!) RoIAlign for rotated rois . Not recommended before my checkout .

Code for skew-bboxes NMS calculation. GPU and CPU are all supported now.

Replaceable and faster implemention for conv.Directly apply to replace existed conv layer.
bug: not support apex mix precision training or half, in debuging.

Rotated conv layer.
Test demo also included for MNIST.(I've fixed a bug and made it supportable for pytorch with version higher than 1.0.0.)

Tested on pytorch 1.1+ with CUDA 9.0. The code is helpful to achieve ATSS with rotation bound boxes.