3.1.1

Monkeypatched over a markdown syntax ambiguity that resulted in an exception when when a square-bracketed link without a shortcut identifier is encountered, e.g.

Oh my god, look at [her butt].

According to Daring Fireball markdown syntax, a link reference may omit the shortcut identifier if it's desired to use the original text as the reference, but the empty square brackets still must be included, e.g.

Oh my god, look at [her butt][].

[her butt]: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjxjMnL2JLPAhXKQCYKHfFVAR0QyCkIITAA&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DLDZX4ooRsWs&usg=AFQjCNHb65jFtOPwGi7HZITW5qJ2PBlURA