Added append/prepend filters

lib/liquid/standardfilters.rb

@@ -103,7 +103,17 @@ module Liquid
     # remove the first occurrences of a substring
     def remove_first(input, string)
       input.to_s.sub(string, '')      
-    end            
+    end             
+                              
+    # add one string to another
+    def append(input, string)
+      input.to_s + string.to_s
+    end
+                                
+    # prepend a string to another
+    def prepend(input, string)
+      string.to_s + input.to_s
+    end
                                              
     # Add <br /> tags in front of all newlines in input string
     def newline_to_br(input)        

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)