Add basic comment support

This adds basic support for listing comments. It's ugly (CSS-wise) but I think it's a decent starting point.

A few questions:

1. Where should extra styling go? I stuck it inline, but I know this probably isn't a good idea.
2. What are some thoughts on making it completely JS? Basically what I hacked together just kind of funnels everything through the backend, but it's not really necessary.

Thanks!