Add top-level setup.py

[chajath]

With this, we can now pip install directly from the repo dir.

See #35.

We can potentially package up experiments as an extra installable (i.e., via huggingmolecules[experiments]). I will do in a follow-up if necessary.

[panpiort8]

Thank you very much for the engagement!
The code looks good, but the PR indeed needs some more work to sew it up:

• update Installation guide in README.md,
• as you suggested, package the experiments module.

If you are willing to do the tasks, I'll be really glad :) if not, simply let me know, and I will take this PR over.

[chajath]

Hi! Sorry I won't have the bandwidth to follow up on the changes. Please feel free to take this PR over.

Thanks!