Redesign durable column to be more a 'mini conpherence'
Summary:
Since I plan to add collapsing, this widens the chat window and moves the switcher to the side, for more visual space for conversation.
TODO: make a magical minimizer so I can always have it open.
Test Plan:
Tested on my large display and little Macbook.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D16635