Editing previous message within timeframe.

Here is the code for editing a message using the up (or down) key. The workflow is as follows:

* Send message to room.
* Notice typo
* Press up
* Fix the typo in the message box
* Resend the message
* Edited message is displayed to users

Once message is edited, users can click on the pencil icon to see what the message used to say. The icon also serves to indicate that the message was edited.

I had to make some large-ish structural changes to the Html of the room to accommodate the icon and the history box. They don't change the general structure of the html, they simply allowed me to position the Absolute box over the content.