setup.py is outdated and does not install all the necessary scripts or packages

[pettyalex]

Hello,

It seems like setup.py has not been maintained as MetaXCan has been extended and improved. It would make MetaXCan way easier to distribute and install if it were installable.

Some problems that I've noticed include:

1. software/PrediXcan.py does not have a shebang to allow it to be executed
2. setuptools.setup in setup.py does not include metax.predixcan or metaxcan.genotype packages, so they aren't installed when calling setup.py
3. Predict.py is not installed
4. The dependencies in setup.py seem out of date
5. Some of the top-level scripts directly import each other (PrediXcan.py imports Predict.py and PrediXcanAssociation.py)

Would you be interested in fixing these problems? I could make a PR that gets MetaXcan ready to publish on PyPI, and I've already started doing some packaging work to get it on bioconda. Thoughts?