WIP: Add windups to incoming messages.

[judytuna]

This winds up messages that are older than 5 minutes. However, the performance is terrible.

[sgwilym]

I think we'd only want to see this effect on the very last message. Here's how I'd go about it personally:

• In Message, wrap the rendering of ActionisedMessage in <WindupChildren>.
• Add a isLastMessage prop to Message
• Make it so that if isLastMessage is true, the skipped prop on WindupChildren is true
• Using the index of a doc when MessageList renders all the docs using docs.map, determine whether the doc being mapped over is the last one, and pass that to the new isLastMessage prop you added to Message.