Making tests more robust to timezone differences
Fixing Sqlite tests for eager loading when using identifier quoting
Adding tests for save and delete when using composite keys
Enabling th emarshaller to load many to many associations with composite
keys
Making Table::primaryKey optionally return string.

Now that all tests passes with it returning array, changing this back so
it returns a single string in cases the is only one key in the array.
This is so becuase otherwise we would make most people life misserable
when interacting with this method and having a database without
composite keys.
No need to skip these tests anymore