Add Python triple-quoted strings "known failure" (#1449)

* Add example of failure in Python parser

Author: brandon-rhodes

examples/prism-python.html

@@ -48,4 +48,17 @@ <h2>Full example</h2>
         return (copy[size/2 - 1] + copy[size/2]) / 2
 if __name__ == '__main__':
     import doctest
-    doctest.testmod()</code></pre>
+    doctest.testmod()</code></pre>
+
+<h2>Known failures</h2>
+<p>There are certain edge cases where Prism will fail.
+	There are always such cases in every regex-based syntax highlighter.
+	However, Prism dares to be open and honest about them.
+	If a failure is listed here, it doesn’t mean it will never be fixed. This is more of a “known bugs” list, just with a certain type of bug.
+</p>
+
+<h3>Triple-quoted strings with what look like strings inside</h3>
+<pre class="language-python"><code>def antique(string):
+    """Replace anachronistic Latin "j" with "i"."""
+    return string.replace("j", "i").replace("J", "I")
+    </code></pre>