extract flatten_arranged_nodes

this is the part responsible for taking a tree and producing an array of nodes
with the parent node before the children

Since children is always a hash, this will never enter the sorting code
and never require the block. so the sorting and the &block was dropped.

This works because ruby enumerates the hashes with insert order (no need to sort again)

lib/ancestry/class_methods.rb

@@ -62,6 +62,20 @@ def arrange_nodes(nodes)
       end
     end
 
+    # convert a hash of the form {node => children} to an array of nodes, child first
+    # modifies input hash
+    #
+    # @param arranged [Hash{Node => {Node => {}, Node => {}}}] arranged nodes
+    # @returns [Array[Node]] array of nodes with the parent before the children
+    def flatten_arranged_nodes(arranged)
+      arranged.inject([]) do |sorted_nodes, pair|
+        node, children = pair
+        sorted_nodes << node
+        sorted_nodes += flatten_arranged_nodes(children) unless children.blank?
+        sorted_nodes
+      end
+    end
+
      # Arrangement to nested array for serialization
      # You can also supply your own serialization logic using blocks
      # also allows you to pass the order just as you can pass it to the arrange method
@@ -105,12 +119,7 @@ def sort_by_ancestry(nodes, &block)
         arranged = arrange_nodes(presorted_nodes)
       end
 
-      arranged.inject([]) do |sorted_nodes, pair|
-        node, children = pair
-        sorted_nodes << node
-        sorted_nodes += sort_by_ancestry(children, &block) unless children.blank?
-        sorted_nodes
-      end
+      flatten_arranged_nodes(arranged)
     end
 
     # Integrity checking