replaced Vertices() with DuplicateVertices()

http://www.grasshopper3d.com/group/ladybug/forum/topics/honeybee-energy-modeling-object-has-no-attribute-error?commentId=2985220%3AComment%3A1149680&groupId=2985220%3AGroup%3A658987
@chriswmackey if you remember we had this issue before too. Let's not
use Brep.Vertices and use Brep.DuplicateVertices instead.