Performance hardening for production

 - Add node-toobusy.  Configure to send 503's to non-superusers for any
   page load when the server gets too busy, to prevent lockup.
 - Sockets are trickier, as we presume continuity of state and can't
   just drop messages with the same impunity.  As a compromise, refuse
   to broadcast chat from non-admins and all blur/focus messages from
   any user when the server is too busy.  Add UI to inform users that
   their messages are not going through.
 - Remove requirejsMiddleware from express.  Production environments
   should now call ``bin/compile-assets.js`` to do asset compilation
   on any code change.  Attach that script to the ``postinstall``
   handler in package.json so that assets are compiled with any
   invocation of ``npm install``.
 - Add ``node-memwatch`` configuration, but since the most useful
   feature (heap diffs) has negative performance implications, only use
   it when environment variable NODE_DEBUG_LEAKS === "1".
 - Remove unnecessary logging.
 - Remove no-longer-used CORS middleware.
Travis copy conf before npm install
Merge branch 'memleaks' of github.com:drewww/unhangout into memleaks