Python bindings implemented

Looks like a couple people have requested python bindings. I came here to do the same a couple days ago, and figured I'd give it a try myself.

I've managed to implement bindings for CascadedCompressor and CascadedDecompressor at https://github.com/carsonswope/py-nvcomp. I plan to implement the other high-level compressor types at some point as well.

It's my first time writing c++ bindings for python, so I'd appreciate a code review from anyone who has a bit more experience. Specifically I wonder if I'm correctly passing void* and other CUDA types between python and c++? I'm sort of assuming the pointers will all be 64-bit, which is okay because I think CUDA only runs on 64-bit?

Also, I'm happy to integrate my code into this repo, just would need some guidance on where to put it, etc.

Cheers!