Remove unused parent-routes handling from vulcan-lib
Remove unused parent-routes handling from vulcan-lib

Vulcan-lib has the notion of routes being a tree. But it's completely
unused, there's a comment suggesting it's not actually fully
implemented, and we definitely broke it with our react-router-wrapper
stuff. So take it out.

Discordius/Lesswrong2,Discordius/Telescope,Discordius/Telescope,Discordius/Telescope,Discordius/Lesswrong2,Discordius/Lesswrong2,Discordius/Telescope,Discordius/Lesswrong2