Display more data for issues and issue views

This even includes displaying issues and comments! Notable caveats for this PR are

* Issue display code isn't as polished as I'd like
* Rendering an issue takes at least 2 API requests, but likely more due to the next caveat. We should discuss if and how we want to batch up API requests for the client.
* We're going to have to do a LOT of markdown render requests. We should seriously consider adopting a JS Markdown lib like https://github.com/chjj/marked
* The client app.js file is getting bloated. I want to refactor it and break stuff into cleaner pieces.
* No tests