Add CCRect::unionWithRect
Add a new CCRect utility function called 'unionWithRect' which computes the minimum rectangle that contains the current rectangle and another given rectangle, similar to to the following .NET function: http://msdn.microsoft.com/en-us/library/ms521839.aspx
Merge pull request #3055 from DarraghCoy/add_rect_union_with_rect

Add Rect::unionWithRect