naive attempt to fix the implode method on stringable

lib/treat/entities/entity/stringable.rb

@@ -58,31 +58,29 @@ def inspect
    end
 
   # Helper method to implode the string value of the subtree.
-  def implode
+  def implode(value = "")
 
     return @value.dup if !has_children?
 
-    value = ''
-
     each do |child|
 
       if child.is_a?(Treat::Entities::Section)
-        value += "\n\n"
+        value << "\n\n"
       end
 
       if child.is_a?(Treat::Entities::Token) || child.value != ''
         if child.is_a?(Treat::Entities::Punctuation) ||
           child.is_a?(Treat::Entities::Enclitic)
           value.strip!
         end
-        value += child.to_s + ' '
+        value << child.to_s + ' '
       else
-        value += child.implode
+        child.implode(value)
       end
 
       if child.is_a?(Treat::Entities::Title) ||
         child.is_a?(Treat::Entities::Paragraph)
-        value += "\n\n"
+        value << "\n\n"
       end
 
     end