Some modernization and tidying up

[fgregg]

Hi Jacob,

this PR

• brings in schema updates from propublica
• uses black and isort to tidy up the code formatting
• fixes all the current flake8 failures
• points the IRS S3 bucket to Giving Tuesday's S3
• Brings back file downloads
• Gets tests working
• And sets up github action CI

@asuozzo, lmk if your repo is actually the one I should be making a PR against.

[asuozzo]

Whoops, super delayed response here, but this is great @fgregg! I've been keeping our branch updated as needed for my purposes but have utterly failed to do much in the way of testing and/or PR any changes back into this repo, so I appreciate this!

One general thought I have here is that it's fantastic that the GivingTuesday bucket exists, but since it's not an IRS resource, I wonder if it makes sense to make irsx more data-source-agnostic, with an easy option to toggle the GT bucket as the default data source. This is probably a longer-term conversation (I don't want to hold up updates that get irsx working right out of the box), but something I've been thinking about.

[fgregg]

@asuozzo so should your fork be the one to make against?

[asuozzo]

@fgregg nope, I think keeping it here is good (if @jsfenfen agrees!)