This release mostly focus on extending the CI testing and restoring broken backward compatibility.

• Add CI test coverage for Rails 3-6 and Ruby 2.2-2.7 (#72) [@mberlanda]
• Add CI mysql test coverage (#74 #75 #76 #77) [@mberlanda]
• Restore rails < 5 mysql support (#78) [@mberlanda]
• Add CI postgresql test coverage (#79) [@mberlanda]

Replace 'type_cast_from_column' to support Rails 6.1 (#68) [@zjohl]

Bugfix:

• Worker options ignore: false and update_duplicates: false cause an error when using postgresql_adapter (#60) [@torce]

• Abstract database-specific statements (#46) [@sobstel]
• Allow to update duplicates on conflict in PostgreSQL (#40) [@sobstel]
• Add CI on pull requests / merges (#38) [@mberlanda]

• Reduce requirements to allow rails 3 (#31) [Dmitry Ishkov]
• Add backticks around "on duplicate key" columns (MySQL) (#33) [Mauro Berlanda]
• PostgreSQL option to return primary keys (#32) [Peter Loomis]

• Support Mysql2 adapter (@varyform)
• Add support for update_duplicates (@mstruve)
• Add support for PostGIS, Mysql2Spatial (@knu)

• "Ignore" support for SQLite [@jfiander]
• "Ignore" support for PostgreSQL [Mauro Berlanda]
• add a callback for before_save [René Sprotte]

This version better supports Rails 5 (thanks @bencolon!) and adds an option for ignoring errors on insert (thanks @lumine!).

Adds support for an "after save" callback on the worker. (Thanks @lukeledet!)

Fix Rails 5.0 deprecation (thanks @huacnlee!)