added a note about how to use quotes in strings (closes #973)

doc/templates.rst

@@ -569,8 +569,9 @@ exist:
 
 * ``"Hello World"``: Everything between two double or single quotes is a
   string. They are useful whenever you need a string in the template (for
-  example as arguments to function calls, filters or just to extend or
-  include a template).
+  example as arguments to function calls, filters or just to extend or include
+  a template). A string can contain a delimiter if it is preceded by a
+  backslash (``\``) -- like in ``'It\'s good'``.
 
 * ``42`` / ``42.23``: Integers and floating point numbers are created by just
   writing the number down. If a dot is present the number is a float,

test/Twig/Tests/LexerTest.php

@@ -150,7 +150,21 @@ class Twig_Tests_LexerTest extends PHPUnit_Framework_TestCase
         $this->assertEquals(922337203685477580700, $node->getValue());
     }
 
-    public function testString()
+    public function testStringWithEscapedDelimiter()
+    {
+        $tests = array(
+            "{{ 'foo \' bar' }}" => 'foo \' bar',
+            '{{ "foo \" bar" }}' => "foo \" bar",
+        );
+        $lexer = new Twig_Lexer(new Twig_Environment());
+        foreach ($tests as $template => $expected) {
+            $stream = $lexer->tokenize($template);
+            $stream->expect(Twig_Token::VAR_START_TYPE);
+            $stream->expect(Twig_Token::STRING_TYPE, $expected);
+        }
+    }
+
+    public function testStringWithInterpolation()
     {
         $template = 'foo {{ "bar #{ baz + 1 }" }}';