Add option to not automatically hook window.resize

It can be useful to remove the responsibility to resizing from the fullcalendar control and instead have the developer manually trigger the required 'render' whenever /she/ deems that a resize happened. Consider cases where resize should only be triggered on a debounce because of complicated sizing code, or cases where the new size of the calendar component is dependent on the *manually computed* value of parent container.

In these cases, fullcalendar is inefficient because in effect the resize event is being triggered way too often.

This pull request simply delegates the responsibility to resize to the user of the fullcalendar control.