code: function(req) {
      var fields = {};
  
      // Fields
      if (_.isString(req.query.fields)) {
        _.forEach(req.query.fields.split(','), function(field) {
          fields[field] = 1;
        });
      }
  
      return fields;
    }
docs: Parses the request query string for `fields`
  
  Converse it into a Mongo friendly `fields` Object
  
  Example: `?fields=hello,world,foo.bar`
  
  @param {Object} req
  @return {Object}