Use NNPDF servers to upload packages
Created by: Zaharid
Upload packages to <packages.nnpdf.science> rather than to my personal server. This is working now, but every user will have to change the channels, as well as the other repos and the installer scripts, so it may be good to merge all at once. I have kept the old key in travis so it is still working as before at the moment.
Closes #407 (closed).