0.5.3 maintenance release
Serialize Python sets to JSON lists.
Support frozenset, too
Releng for 0.5.4
Merge branch 'maint'
Changelog next
Merge branch 'master' into next

Conflicts:
	CHANGELOG.rst
Fix a double fault in the Visitor

KeywordExceptionFormatError was caught; fix up the exception code to
pass the right format strings in.
Coming soon: bool(Record) to determine NULL-ness