Fixes #28.
First steps at getting chat to scroll. Extracted the chat input form into separate view, so it's not in the scrolling container.
Properly moves to the bottom on new messages now.
Fixed bottom scroll limit, so chat doesn't go under the input.
Fixed some spacing issues and blocking. Input now covers up text that scrolls underneath it.
Some progress on #31
Changed middle chat width to make space for a scroll bar if necessary.
Fought a holy war with overflow-x/y and failed. Relented and just made things tighter in the x axis to make room for scroll bars on both chat + presence gutter.
Merge branch 'chat-scroll'

Fixes #31 to a first approximation and closes #20.