Add modulo filter

lib/liquid/standardfilters.rb

@@ -218,6 +218,10 @@ module Liquid
       to_number(input) / to_number(operand)
     end
 
+    def modulo(input, operand)
+      to_number(input) % to_number(operand)
+    end
+
     private
 
       def to_number(obj)

test/liquid/standard_filter_test.rb

@@ -173,6 +173,10 @@ class StandardFiltersTest < Test::Unit::TestCase
     assert_template_result "Liquid error: divided by 0", "{{ 5 | divided_by:0 }}"
   end
 
+  def test_modulo
+    assert_template_result "1", "{{ 3 | modulo:2 }}"
+  end
+
   def test_append
     assigns = {'a' => 'bc', 'b' => 'd' }
     assert_template_result('bcd',"{{ a | append: 'd'}}",assigns)