Make ui_calculator a Python package

[MaxGhenis]

Thanks for the great scripts! I wanted to use them in a package without relying on running it from the right folder structure, so added the necessary components to make it installable. Here's a full set of changes:

• Make ui_calculator package using setup.py and reorganizing files as required for packaging.
• Add a simple pytest test, checking that the function produces the expected result on the sample yearly data
• Update all examples to use the package
• Various code style and typo fixes (e.g. ensuring 80-character lines)
• Add GitHub's default Python .gitignore and remove .pyc file which is typically ignored for GitHub

You can see it in action in this Colab notebook, which installs the package from GitHub, loads sample data from GitHub, and runs the code to calculate benefits.

[MaxGhenis]

Hi - just wanted to check in here on this. Is this something the maintainers are interested in? If so I can resolve the merge conflicts.

[ganong123]

@MaxGhenis I'm sorry for the delay. Yes, this is a fantastic change. please do resolve the merge conflicts and then I will go ahead and merge.

[ganong123]

Also, I never knew about colab before and have never made a package before. good stuff!

FYI @peterobertson we will likely want to eventually update the R scripts that call Python in covid_inc_sprt to capture this change in ui_calculator

FYI @roshanm9 I do not think we need to update https://github.com/ganong-noel/ui_rep_rate

[MaxGhenis]

Thanks @ganong123, I resolved the merge conflicts and verified the tests run locally, so this is now ready to go.

I also added a GitHub Action to automatically test in pull requests, and a badge to show the build status, but it looks like that will only take effect in a subsequent PR. It usually activates within the PR it's added to, but might not here because GitHub Actions haven't been activated in the repo, or because I don't have write access.

[MaxGhenis]

The GitHub Action for testing works on my branch: https://github.com/MaxGhenis/ui_calculator/actions/runs/253051908

[ganong123]

@MaxGhenis thanks for your work here!