Hot reload: refresh comments automatically and some bugfixes relating to statefulness

State management is a bit of a mess at the moment. I've tried to clear it up here and integrated a lightweight virtual DOM (morphdom) to be able to update comments, etc by diff-ing between the expected comment list and the actual one.

This means when new comments come in live, replies still being written in textboxes are unaffected.

Fixes #318

I've also incorporated WebSockets into here - clients will connect and subscribe for updates to the page they're on. If there's a new comment/edited comment/upvote/deleted comment event, it will pull the new comments in from the server, then update the comments shown using the above virtual DOM diffing technique.