Feature/update reqs and add simple test

[paulf81]

This pull requests adds/improves some software components ahead of the v1 changes.

It addresses: Issue #34 and Issue #31 , changes include:

1. Removing unused requirements
2. Adding semantic versioning using compatible release specifier
3. Adds a first pytest, which just declares an empty py-sim but can test everything imports
4. Adds a continuous integration workflow for automatic testing
5. Removes un-used requirements.txt
6. Adds vs-code items to gitignore

Pulling to main to cause the ci to go into effect and can back merge to develop after

Pull request closes #34 and closes #31

[misi9170]

Looks good---might have to get this onto main and then fix any possible bugs if they come up, because I'm not sure how to test any of this really. But good to start on the CI path for Hercules

[paulf81]

I ran the tests locally (and I think this pull request ran the tests too), but yeah, might also be different after merging...

[genevievestarke]

Looks good to me!

[paulf81]

Merging!