Update date to accept epoch

lib/liquid/standardfilters.rb

@@ -158,6 +158,10 @@ module Liquid
         return input.to_s
       end
 
+      if ((input.is_a?(String) && !/^\d+$/.match(input.to_s).nil?) || input.is_a?(Integer)) && input.to_i > 0
+        input = Time.at(input.to_i)
+      end
+
       date = input.is_a?(String) ? Time.parse(input) : input
 
       if date.respond_to?(:strftime)

test/lib/liquid/standard_filter_test.rb

@@ -97,6 +97,9 @@ class StandardFiltersTest < Test::Unit::TestCase
     assert_equal "07/16/2004", @filters.date("Fri Jul 16 01:00:00 2004", "%m/%d/%Y")
 
     assert_equal nil, @filters.date(nil, "%B")
+
+    assert_equal "07/05/2006", @filters.date(1152078955, "%m/%d/%Y")
+    assert_equal "07/05/2006", @filters.date("1152078955", "%m/%d/%Y")
   end