adding concat filter to append arrays

lib/liquid/standardfilters.rb

@@ -177,6 +177,10 @@ module Liquid
       input.to_s + string.to_s
     end
 
+    def concat(input, array)
+      InputIterator.new(input).concat(array)
+    end
+
     # prepend a string to another
     def prepend(input, string)
       string.to_s + input.to_s
@@ -344,6 +348,10 @@ module Liquid
         to_a.join(glue)
       end
 
+      def concat(args)
+        to_a.concat args
+      end
+
       def reverse
         reverse_each.to_a
       end