code: function (appIdOrSlug, params) {
      var path = this.constructPath(constants.APPS, appIdOrSlug);
      return this.Core.GET(path, params);
    }
docs: Get an app
  @param  {String|Integer|undefined} appIdOrSlug A Robin app identifier or slug
  @param  {Object|undefnied}         params      A querystring object
  @return {Function}                             A Promise