Create test suite generator (requires per-exercise templates)

[cmccandless]

Using the WIP extension instead of draft PR so that CI scripts will run on these changes.

[cmccandless]

Example template for two-fer

[yawpitch]

Since we're configuring flake to an 80 character limit we should do the same with black ... by default it's 88 characters and there will be occasional disconnect.

[yawpitch]

Overall I think this is a sensible approach that will get us up and moving quick. I feel like my approach would play out better in the long run, but I'm willing to abandon it for now. Did suggest some small changes though.

[cmccandless]

Since we're configuring flake to an 80 character limit we should do the same with black ... by default it's 88 characters and there will be occasional disconnect.

I followed black's recommendation on this; line length is still 80, but there's a tolerance of 10%.

[yawpitch]

As is I'm happy to merge this and continue (though a few more docstrings would be nice).

[yawpitch]

I do think that a slight modification of my branches generate.py file could possibly be used to create a pretty good rough pass of the template text for quite a number of exercises, BTW.

Hmm ... actually maybe bypass that idea ... I don't see a foothold in jinja2 for getting the post-macro resolution, pre-render template.

[cmccandless]

though a few more docstrings would be nice

Done.

[yawpitch]

Looks good.