style(rxApp): Add styles and documentation for Account Info box

Closes #555.

See https://jira.rax.io/browse/EOD-2
So this has gotten me in the past ([twice](https://github.com/rackerlabs/encore-ui/issues/256) [actually](https://github.com/rackerlabs/encore-ui/issues/251)): Using the 'title' attribute will cause the browser to show a title popup whenever the mouse is over the panel. Instead, I'd use a name like `panel-title` or `heading`