Colinmacdonald/17 render url

Closes #6
Closes #20
Closes #17 

- Adds a default chat example
- Fixes avatars to fit the default 25x25 style.
- Adds link and img support.
- Refactors view and tests
- Fixes IE8 bugs:
 - removes the use of getElementsByClass (unsupported in IE8)
 - adds type="button" to prevent enter input keydowns clicking the button and causing duplicate messages in IE8