Release 2.9.1

Update composer.json

Allow installation with DataModel 8.x

Fix 2.7.0 release date (today)

Release 2.6.0 (#237)

Merge pull request #234 from wmde/rel250

Release 2.5.0

Merge pull request #218 from wmde/release240

Release 2.4.0

Release 2.3.0 (#213)

Merge pull request #195 from wmde/release220

Release 2.2.0

Update release notes for 2.1.0