added unit test for hash propagation through boxes
added unit test for hash propagation through boxes

andrewkaufman/gaffer,boberfly/gaffer,GafferHQ/gaffer,appleseedhq/gaffer,paulondc/gaffer,andrewkaufman/gaffer,davidsminor/gaffer,appleseedhq/gaffer,boberfly/gaffer,goddardl/gaffer,johnhaddon/gaffer,lucienfostier/gaffer,appleseedhq/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,chippey/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,ivanimanishi/gaffer,cedriclaunay/gaffer,chippey/gaffer,paulondc/gaffer,davidsminor/gaffer,ivanimanishi/gaffer,boberfly/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,johnhaddon/gaffer,davidsminor/gaffer,hradec/gaffer,hradec/gaffer,cedriclaunay/gaffer,goddardl/gaffer,hradec/gaffer,GafferHQ/gaffer,chippey/gaffer,lucienfostier/gaffer,andrewkaufman/gaffer,cedriclaunay/gaffer,chippey/gaffer,hradec/gaffer,lucienfostier/gaffer,paulondc/gaffer,GafferHQ/gaffer,ivanimanishi/gaffer,goddardl/gaffer,ImageEngine/gaffer,paulondc/gaffer,ImageEngine/gaffer,cedriclaunay/gaffer,hradec/gaffer,GafferHQ/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,boberfly/gaffer,davidsminor/gaffer,lucienfostier/gaffer,ivanimanishi/gaffer,goddardl/gaffer