Upgrade to Ruby 2.1.5
re-remove author groups and message participants from schema
[#79321200][bugfix] Show long title in the Workflow
Merge pull request #636 from Tahi-project/ruby_2_1_5

Upgrade to Ruby 2.1.5
Consistantizeificate attachment thumbnail implementations
Merge pull request #646 from Tahi-project/attachment_thumbnail_consistantification

Consistantizeificate attachment thumbnail implementations
Merge branch 'master' into squash-migrations