Upload to pip

[lavagetto]

It would be awesome to be able to install gnlpy via pip, that would help production installations wherever pip is allowed, or just unit testing/ci for projects that do use gnlpy. I think that's a better alternative compared to using git submodules, which is what I am going to do at the moment if gnlpy is not uploaded to pip

[chantra]

Based on current master: https://pypi.python.org/pypi/gnlpy

[lavagetto]

@chantra @vmauge thanks!