Summary:
Add cudnn v6 support, including testing support for dilated convolution.
Add a check to ensure that the versions of cuDNN used to compile Caffe2 and run it are compatible
Closes https://github.com/caffe2/caffe2/pull/85
Reviewed By: bwasti
Differential Revision: D4387690
Pulled By: Yangqing
fbshipit-source-id: 312960134398dd4afe6ee0c01cdc160046c904e8