Fix #1175 -- add support for Markdown extensions.

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
use one FakeSite; fix bugs in markdown plugin magic

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
Merge pull request #1176 from getnikola/markdown-extensions

Fix #1175 -- add support for Markdown extensions.