fix markdown regressions from switch to mistune

[mattbk]

http://inside.gratipay.com/howto/build-gratipay

[chadwhitacre]

:-(

I also noticed --- on http://inside.gratipay.com/big-picture/welcome not getting turned into — (mdash).

It's something to do with a change in markdown renderer, I think.

@techtonik Weren't you involved with that? Do you remember what change we made?

[mattbk]

As well as http://inside.gratipay.com/howto/tell-people-about-gratipay, but I imagine several pages have issues.

[chadwhitacre]

For the --- the issue is that we never reimplemented SmartyPants when switching to mistune (#339; cf. lepture/mistune#57). Not sure about the HTML leakage ...

[chadwhitacre]

@techtonik Are you able to work on this?

[chadwhitacre]

https://pypi.python.org/pypi/smartypants/

Does it match what we were getting from Hoedown via misaka?

[techtonik]

@whit537 sorry, I got ill - a week with temperature, and nerve in my right hand is aching so it is very painful to type. I hope that it will be better tomorrow. To catch things like this early we should add spider test like awesome-bot for links. Also I don't see where this build page is linked from through google info: query.