Models on Zenodo or another safe repository

[genisplaja]

Alright:

• First we had the pre-trained weights included in the package, but that made it really heavy.
• Next, we moved those to Google Drive, and these are download using gdown when a model is initialized.
  I think Google Drive is a good patch for now but it's not the appropiate way. Maybe we should use Zenodo or some similar repository to safely store the weights online, retireve them from there, and that would allow a better tracking of different versions.

Maybe then we should allow load_model() to have a version argument so that users can initialize the different versions online, and always default to the last one.