* Issue 20: Repetitions incorrectly allowing null subtokens
* Issue 22: REFs don't have standard attributes (like grammar_name)
* Issue 23: EXCEPT stops after first successful match, even if it doesn't
meet other criteria
* Issue 24: hash() breaks on recursive grammars after grammar_resolve_refs
* Issue 25: WORD("^") does not work as expected
* Fix a leftover reference in the docs to find_tag* methods
* Add a few missing attributes to classdict_map