Sort + CUB templates (Discussion + Work in Progress)

Hi,

I would like to discuss the possibility of including [CUB](https://github.com/NVlabs/cub) templates into cutorch. We can use it for implementing things like sort in CUDA. The easiest way I have found is to just copy-paste the sub-directory containing the C++/CUDA templates in lib, but it is still very large (1.5MB). The submodule approach is worse as it includes the entire repository (40MB). 

This is what I intend to use for cutorch.sort: http://nvlabs.github.io/cub/classcub_1_1_block_radix_sort.html#aa6b164f496c319269f83502d7fc53512.

Before I start working on it, I would like your opinion concerning the inclusion of CUB.