The routes for categories are changing. The scheme that I intend to move
us to is:
/c/*slug_path/(:id)/ENDPOINT
/c/*slug_path/(:id)
This commit adds support for the new scheme to the server side without
dropping support for existing URLs. It is necessary to support existing
URLs for two reasons:
* This commit does not change any client side routing code,
* Posts that contain category hashtags that refer to a root category
are baked into URLs that do not fit this new scheme, (/c/[id]-[slug])
d84c34ad75