Heap#consolidate: Use compare_fn instead of #==

Fix #23.

Author: bcc32

lib/containers/heap.rb

@@ -369,7 +369,7 @@ def consolidate
           degree += 1
         end
         degrees[degree] = root
-        min = root if min.key == root.key # this fixes a bug with duplicate keys not being in the right order
+        min = root if !@compare_fn[min.key, root.key] # this fixes a bug with duplicate keys not being in the right order
       end
     end
     @next = min