get(path) {
    var indexInUrls = this.urls.indexOf(path);

    if (indexInUrls === -1) {
      return;
    }

    if (this.replacementUrls.length) {
      return new Promise(function (resolve, reject) {
        resolve(this.replacementUrls[indexInUrls]);
      }.bind(this));
    } else {
      return this.createUrl(path);
    }
  }
Get a URL for a resource
@param  {string} path
@return {string} url