updated composer.json.
added group trait to find statement.
fixed some doc blocks.
added group by tests.
change double to single quotes.
remove support for a comma separated list of group by fields as it's not abstracted enough.
Refert commits introducing old code and re-fix issue, this time cleaning up unnecessary code.
Merge pull request #24 from treshugart/GH-23

Fix issue causing transaction errors #23.