Remove unnecessary comment, there is now a unittest for this condition.
Update function docs for _parsers._is_allowed() function.
Move allowed_options into separate groups in their own functions.
Add _parsers._is_string() function, and change _sanitise() to use it.
Update _parsers._sanitise_list() documentation.
Add _parsers.GenKey.secring and _parsers.GenKey.keyring attributes and docs.
Fix upstream issue #62, handle expired keys.

 * see https://code.google.com/p/python-gnupg/issues/detail?id=62