addLoop(loop) {
    return new Promise(resolve => {
      this.loops.push(loop);
      resolve(loop);
    });
  }
@method addLoop
@description Adds loop to this app.
@param {Object} loop - the loop to add
@return {Promise} Promise that is resolved when promises completed.
@memberof module:core.App
@example <caption>Adding a loop to an app</caption>
const loop = new Loop(() => {
 // ...
});

const app = new App();

app.addLoop(loop);
loop.start();