handleSuspension = function() {
          self.state = 'suspended';

          if (self._resumeAfterSuspend) {
            delete self._resumeAfterSuspend;
            self._autoResume();
          }
        }
Automatically suspend the Web Audio AudioContext after no sound has played for 30 seconds.
This saves processing/energy and fixes various browser-specific bugs with audio getting stuck.
@return {Howler}