Make message content editable field

[metasean]

• [ ] Ensure XSS safe.
• [ ] Ensure code snippets play nice.

[metasean]

• [ ] Ensure this fixes mobile Chrome's issue with navigating to editable text that isn't currently visible in the textfield.

[metasean]

• [ ] Detect http:// or https:// and turn it into a tag so it is clickable