Added ngGridItem unit tests.
Added ngGridItem unit tests.

BTMorton/angular2-grid,aebsubis/angular2-grid,aebsubis/angular2-grid,BTMorton/angular2-grid,ankitw77/angular2-grid,ankitw77/angular2-grid,ankitw77/angular2-grid,aebsubis/angular2-grid,BTMorton/angular2-grid