Index pip-installed packages

[hoodmane]

This isn't very efficient, we should use pep 658 metadata which pypi provides now so we don't have to redownload the wheel. Also we should do fetches concurrently and asyncio.gather them. But it gets the basic idea.

Would resolve #107.

cc @jaraco @ryanking13 do either of you see anything wrong with this concept?

[jaraco]

See #110 where I've done some work to refactor the functionality to make it easier to alter behavior such as proposed here.

[hoodmane]

Yeah thanks for the review, this is definitely a DO NOT MERGE pr. The point is that it passes the one test in the worst possible way and gives us a baseline for writing a good implementation.