Add functionality to export a dataframe into a .pdb file

[mgiammar]

This PR adds the mmdf.write function which permits the export of a pandas DataFrame object to a PDB file. Currently the method only supports writing PDB files since it only creates a structure object with the chains, residues, and atoms; requisite information for populating a mmCIF header is currently absent.

[alisterburt]

@mgiammar sorry for not catching this, not sure how I missed it! What an awesome PR - functionality works great, would be really cool to get mmCIF working too 🙂

I've given you maintainer access to the repo, you should be able to push a tagged commit to main to trigger the deployment workflow

Assuming this remote for this repo is called upstream (standard convention) this should be as simple as...

git checkout main
git pull
git tag -a v*.*.* -m "v*.*.*"
git push --follow-tags upstream main

You should also come join us on the teamtomo zulip! https://imagesc.zulipchat.com/#narrow/channel/426493-TeamTomo

[alisterburt]

@cormsby626 hey look, people on the other side of the world are using your package!