Addition of future as dependency and fix in README.md

[ramaroberto]

Hi guys,

I've just installed your library and I came across a couple of issues. Firstly future should be a dependency since it's been used when trying to run the library with python2. Secondly the text in README.md that says that we should first build the cython extension should be at the beginning of the section. There's few people that are going to find that at the bottom! (I've actually spent 10min looking around why it wasn't working until I checked again and found that bit).

Thanks for the library! I saw the list of kernels and seems awesome :).

Best, Roberto.

[ysig]

Hey!

First of all thanks a lot for contributing.

I will follow your commits in inverse order:

1. I think future was already in the requierements file (correct me if I am wrong).
2. I pushed an ignore file that I had forgot to, that includes what you say.
3. I cherry-picked your change in the Readme file so you are now a contributor!