code: function replaceAssociationPosition(req, res) {
    if(redirect(req.params.id, '../', '/tags', res)) {
      return;
    }
  
    var id = req.params.id;
    var position = req.body.position;
    var rootUrl = req.protocol + '://' + req.get('host');
    var queryPath = req.originalUrl;
    req.chickadee.setAssociation(req, id, null, null, null, position, rootUrl,
                                  queryPath, function(response, status) {
      res.status(status).json(response);
    });
  }
docs: Replace the specified association position.
  @param {Object} req The HTTP request.
  @param {Object} res The HTTP result.