listProjectCards(cb) {
      return this.listProjectColumns()
        .then(({data}) => {
           return Promise.all(data.map((column) => {
              return this._requestAllPages(`/projects/columns/${column.id}/cards`, null);
           }));
        }).then((cardsInColumns) => {
           const cards = cardsInColumns.reduce((prev, {data}) => {
              prev.push(...data);
              return prev;
           }, []);
           if (cb) {
              cb(null, cards);
           }
           return cards;
        }).catch((err) => {
           if (cb) {
              cb(err);
              return;
           }
           throw err;
        });
   }
Get information about all cards of a project
@see https://developer.github.com/v3/projects/cards/#list-project-cards
@param {Requestable.callback} [cb] - will receive the list of cards
@return {Promise} - the promise for the http request