Style the list, dropdown

After #6. @bantic please review and merge if you find it acceptable.

Implements log out, with unit and acceptance tests.
Yes. Calls `window.location =` via https://github.com/aptible/diesel.aptible.com/pull/7/files#diff-53f6d9cb9b83cb8e95328d9f7bc5383cR6 to blow away anything stored locally.