use(fulfilled, rejected, options) {
    this.handlers.push({
      fulfilled,
      rejected,
      synchronous: options ? options.synchronous : false,
      runWhen: options ? options.runWhen : null
    });
    return this.handlers.length - 1;
  }
Add a new interceptor to the stack

@param {Function} fulfilled The function to handle `then` for a `Promise`
@param {Function} rejected The function to handle `reject` for a `Promise`

@return {Number} An ID used to remove interceptor later