prepared the 1.2 release
bumped version to 1.3-DEV
added Dariusz as an author
Add JoinFunctionFixer
feature #771 Add JoinFunctionFixer (keradus)

This PR was squashed before being merged into the 1.3-dev branch (closes #771).

Discussion
----------

Add JoinFunctionFixer

Implement #769

Commits
-------

ac6f1de Add JoinFunctionFixer