Easier way to pin to "latest" release

[asmeurer]

The GitHub tags make it easy to pin to a specific release, but we also need an easy way to pin to the "latest" release. This is needed for the reporting.

One option is to actually release the test suite as a installable package (see #85).

Another idea would be to have a branch, separate from master, that gets updated with the latest tag whenever we release. This is fairly simple but an issue is that it's a quite different release process from any other Python package, so it may confuse people. A package would be a lot less confusing to people.

[asmeurer]

I've already seen people installing from master, and running into bugs that occurred between releases.

[honno]

Well I don't think we're using tag-releases to emphasise stability, so much as using them as semantic breaks for when significant work has been done. Given that we shouldn't intentionally merge broken work into master, the HEAD of master has the same stability guarantees as a tag-release (i.e. we'll unintentionally introduce a bug just as much as we intentionally/unintentionally fix them).

(as an aside I think generating releases automatically after every PR merge would be very nice. something I'll explore if I get the time.)

[asmeurer]

We haven't tagged this repo in a while. If it becomes an issue for an upstream we can start doing it again. Otherwise, people should just keep using master.