Doesn't expose version

[ezyang]

There is no way to tell what the version of ideep is from the library. There should be.

[gujinghui]

@ezyang
the mkldnn-bridge for pytorch/caffe2 is being separate from ideep chainer.
we're reducing the LOC and improving the API only for pytorch/caffe2.
when done, we plan to make the mkldnn-bridge as a part of pytorch/caffe2, instead of a submodule.