Log Message:
updated to 0.17

ChangeLog:
0.17
	- More void context correctness fixes WRT tied values
	- Overzealous seen value mappings made by Callback were removed

0.16
	- Fix passing of void context when visiting hashes/arrays (perf
	  optimization to avoid unnecessary cloning)
	- Added 'visit_seen' and a 'seen' callback for circular structures
	- Class callbacks are now fired from least derived to most derived, not in
	  hash key order