Updated mdx_code to allow {2,} at signs for code syntax highlighting …

…instead of mandating two. The quantity of opening and closing @ signs must match.

Change inspired by mdx_fenced_code.py, at Python Markdown.
http://gitorious.org/projects/python-markdown/repos/mainline/blobs/master/mdx_fenced_code.py

markdown/mdx_code.py

@@ -16,7 +16,7 @@ def extendMarkdown(self, md, md_global):
         md.textPreprocessors.insert(0, preprocessor)
 
 
-CODE_BLOCK_REGEX = re.compile(r"\r?\n(?P<spaces>[ ]*)@@[ ]*(?P<syntax>[a-zA-Z0-9_+-]+)[ ]*(?P<linenos>[a-zA-Z]*)[ ]*\r?\n(?P<code>.*?)@@[ ]*\r?\n", re.DOTALL | re.MULTILINE)
+CODE_BLOCK_REGEX = re.compile(r"\r?\n(?P<spaces>[ ]*)(?P<fence>^@{2,})[[ ]*(?P<syntax>[a-zA-Z0-9_+-]+)[ ]*(?P<linenos>[a-zA-Z]*)[ ]*\r?\n(?P<code>.*?)(?P=fence)[ ]*\r?\n", re.DOTALL | re.MULTILINE)
 
 class CodeBlockPreprocessor :
     def run (self, text):