This reverts commit c99d507f.

default create_with_value to a hash so we can eliminate conditionals, add test surrounding create_with(nil) behavior

Refactor Active Record test connection setup. Please see the RUNNING_UNIT_TESTS file for details, but essentially you can now configure things in test/config.yml. You can also run tests directly via the command line, e.g. ruby path/to/test.rb (no rake needed, uses default db connection from test/config.yml). This will help us fix the CI by enabling us to isolate the different Rails versions to different databases.

Set reverse_order_value when asked to reverse_order().
Do the actual reversal in build_arel.

Evaluate default scopes at the last possible moment in order to avoid problems with default scopes getting included into other scopes and then being unable to remove the default part via unscoped.