Add fallback/failover to polling when push fails

[TPonsky]

When the push service fails, due to bad keys for instance, the chat interface doesn't indicate that there's no push going on so the user just sits there waiting for others to comment and nothing happens. The user doesn't know that they have to refresh the page to get updates. This both very bad and totally fixable. Please add some kind of checking to the chat system that when it can't send the messages to the push service (for whatever reason) that it defaults to the standard functionality so that the user can at least continue to use the tool.