Move functional tests to another sub-folder
Revert to 'rx' instead of 'lrx' (my undoing)
Fix AttributeError for specifying bad mode

An AttributeError was expected, but KeyError is raised.
Catch as KeyError, re-raise as ValueError as originally
intended, but also display the given mode.
Merge pull request #4 from jquast/fix-mode-value-error

Fix helper message when bad mode is specified, tried to catch AttributeError, should catch KeyError.