Integration tests which involve historical stack versions

It'd be great to have some tests which do some sanity checks using older stack versions:

1) Can an old stack version build the current stack version (particularly via `stack upgrade --git`)? (this build works all the way back to the first stable release, 0.1!) - https://gist.github.com/mgsloan/5ba3eb8e3b32ff409a8b

2) Can current stack build an old stack version (particularly, via `stack upgrade --git`). Similarly, we can still build the first stable release.

3) Do any integration tests fail if working directories from the previous stack version are left behind?

4) Test the `require-stack-version` demanded by the `stack.yaml` generated by `stack init`