Updated BoundsNode.retrieve method to work with bounds

The BoundsNode.retrieve method did not take width and height of the lookup item in consideration.

Now it will. When part of the item overlaps multiple child nodes, the contents of all overlapping child nodes are returned, instead of just the one where the top left corner is.
Merge pull request #7 from Qqwy/patch-1

Updated BoundsNode.retrieve method to work with bounds