skip columns named 'lock_version' when automatically rendering fields…

… for all columns in the table (like we skip created_at, etc)

lib/formtastic.rb

@@ -241,7 +241,7 @@ def inputs(*args, &block)
         if @object && args.empty?
           args  = @object.class.reflections.map { |n,_| n if _.macro == :belongs_to }
           args += @object.class.content_columns.map(&:name)
-          args -= %w[created_at updated_at created_on updated_on]
+          args -= %w[created_at updated_at created_on updated_on lock_version]
           args.compact!
         end
         contents = args.map { |method| input(method.to_sym) }