Allow RouteResult to return a view
Added RoutablePage
Fixed broken test

Caused by adding view into RouteResult
Started RoutablePage docs
Improvements to subpage_urls docs
Retitled routable_page doc, added to index
Revert "Allow RouteResult to return a view"

This reverts commit bbbc83c56e9e627160af46061ce0183c23a7e072.
Revert "Fixed broken test"

This reverts commit 911ba9ec0684bc6f68ea80d9b7fe5db267e34fd7.
Rewrote superpage to no longer need core changes
Merge branch 'superpage' of https://github.com/kaedroho/wagtail into kaedroho-superpage
Copyediting of routable_page docs, and longer explanation of what you would use it for
Added routable page to release notes and changelog