Clarify protected routes

[oskarrough]

One thing I noticed refactoring #226 is, that we have a few different ways of authenticating in routes and I wasn't sure which to use when. Maybe we can clarify it and/or refactor if needed.

• mixins/authenticated-route.js (beforeModel hook, transitions to login if not authenticated)
• mixins/owner-route.js (afterModel hook, transitions to login if model!= userChannel
• routes/user-channel.js (uses mixin/authenticated-route)
• this.authenticatedRoute() (from torii, used in router.js. same as authenticated-route mixin?)