feat(girdz): add `shrinkToFit: true` options to the users grid
feat(gridz): very basic example for toggling jqGrid columns
feat(gridz): handy method for checking if a column with the given id is hidden
feat(gridz): more generic method toggling grid's columns visibility
feat(gridz): create simple controller for the grid directive and expose it to the parent scope
chore(gridz): separate file for gridz controller, write some missing specs