[meta] support fenced code blocks

edit

I would like to be able to use fenced code blocks delimited by ``` instead of having to rely on 4-spaces indent.

Askbot seems to be using python-markdown2 internally so the change should be easy enough

This is a code block with multiple lines of code, and it isn't being rendered correctly.

Resources:

• https://askbot.org/en/question/16779/...
• https://python-markdown.github.io/ext...