feat(rendering): Fixes #1488. Bind to resize event

The grid now binds to window resize events and will redraw accordingly.
Also if the grid is less than one row-height tall initially it will resize
itself to fit 10 rows by default. This is configurable with the
minRowsToShow option
feat(scrolling) add a new grid.isScrollingVertically .isScrollingHorizontally flags and set them via debounced function.
feat(gridUtil) added a new debounce function to gridUtil
Merge branch 'master' of https://github.com/angular-ui/ng-grid into 3.0-subgrid
Merge branch '3.0-subgrid' of github.com:yayasoft/ng-grid into 3.0-subgrid