Repobee

This is primarily a maintenance release in preparation for implementing GitLab support. End-user experience is not (well, _should not be_) impacted.

Documentation
* cddb805 Touch up README

Refactorings
* 99d9030 Add students as optional argument to get_repo_urls (186)
* 3518ebc Move token handling for repo urls to the API layer (185)

Other
* aa55df0 Pin repobee-plug version, fix 183
* a89a3aa Make tox pip-install non-editable (182)

Security updates
* ecc35da Use git pull instead of git clone (176)

Documentation
* 8f5d57c Add notes on .com vs Enterprise usage, fix 160
* dd5450f 9f90b85 General documentation updates

Refactorings
* abc9073 Remove redundant validation checks (174)

Features
* 9c8aef4e9f19cc5546cc95047f5eac5088357e79 Add group assignment functionality (166)

Changelog
* 782d4bd53fbfe01739e3a6fd0d74dbd5b85d2487 Fix crash in show-config

Changelog
* c7143b389293236f346d59e30c5497fad1264e9a Repomate changes name to RepoBee! That's all there is to it here.