method fix, remove for delete

lib/classifier/lsi.rb

@@ -85,7 +85,7 @@ def categories_for(item)
     #
     def remove_item( item )
       if @items.keys.index item
-        @items.remove item
+        @items.delete item
         @version += 1
       end
     end
@@ -297,7 +297,7 @@ def highest_ranked_stems( doc, count=3 )
 
     def marshal_dump
       [ @auto_rebuild, @word_list, @items, @version, @built_at_version,
-        @options,
+        @options
       ]
     end
 
@@ -306,6 +306,10 @@ def marshal_load(data)
         @options = data
     end
 
+    def to_yaml_properties
+      %w{ @auto_rebuild @word_list @items @version @built_at_version @options }
+    end
+
     private
     def build_reduced_matrix( matrix, cutoff=0.75 )
       # TODO: Check that M>=N on these dimensions! Transpose helps assure this