v3.0.1

- [Bugfix] fix mysql initialization (#159, #160)
- [Improvement] Better handling of continuous integration
- [Bugfix] fix `tutor --version` (#156)
- [Improvement] Absolute settings imports -- 📯 thanks @tonytan4ever!

v3.0.0: Tutor v3 complete rewrite

Replace all make commands by a single "tutor" binary. Environment and
data are all moved to ~/.tutor/local/share/tutor. We take the
opportunity to add a web UI and revamp the documentation.

This is a complete rewrite.

Close #121.
Close #147.