Repobee-plug

Breaking changes
* cd3e7f9 Refactor generate_review_allocations hook (25)
- The signature and semantics of the hook have changed, see the [docs for details](https://repobee-plug.readthedocs.io/en/latest/code.htmlrepobee_plug.corehooks.PeerReviewHook.generate_review_allocations)

Features
* bdd8530 Move apimeta to repobee-plug (23)

Documentation
* 0b3b8a0 Update documentation for v0.8.0
* dfa8dcd Bump minor version number to 0.7.0 in docs

Other
* 12b213e Fix tag regex in .travis.yml

Features
* fcf21b0 Add extension command hook (22)

Features
* 5116dfa Add API hooks (20)

Other
* 54feed2 Setup tox builds for macOS (19)
* 4785c78 Fix usage of pytest's ExceptionInfo (18)

Bugfixes
* 5f0fc8d Correct bad version number regex, fix 7

Other
* 5ebaac0 Reduce development status from beta to alpha, fix 12

Changelog
* 23f6e4dea6f8e7c507ccf777403a667cdff5135a `repomate-plug` is now `repobee-plug`

Changelog
* 6c28df9ed60dcd8c36d210dba5009d872c1cccb6 Fix an issue related to outdated version of pluggy