Added append/prepend filters

test/standard_tag_test.rb

@@ -393,6 +393,18 @@ HERE
     assert_template_result('321','{%for item in array reversed %}{{item}}{%endfor%}',assigns)    
   end
   
+  def test_append
+    assigns = {'a' => 'bc', 'b' => 'd' }
+    assert_template_result('bcd',"{{ a | append: 'd'}}",assigns)        
+    assert_template_result('bcd',"{{ a | append: b}}",assigns)        
+  end
+  
+  def test_prepend
+    assigns = {'a' => 'bc', 'b' => 'a' }
+    assert_template_result('abc',"{{ a | prepend: 'a'}}",assigns)        
+    assert_template_result('abc',"{{ a | prepend: b}}",assigns)        
+  end
+  
   def test_ifchanged
     assigns = {'array' => [ 1, 1, 2, 2, 3, 3] }
     assert_template_result('123','{%for item in array%}{%ifchanged%}{{item}}{% endifchanged %}{%endfor%}',assigns)