escape characters are not correctly unescaped in URLs

[af4jm]

If I have the following Markdown link...

[YouTube vid](https://www\.youtube\.com/watch?v=2SJ977\-CMPg&t=360)

it should generate the following HTML

<a href="https://www.youtube.com/watch?v=2SJ977-CMPg&amp;t=360">YouTube vid</a>

but instead it leaves the escaping backslashes in, and changes the & to & resulting in a malformed URL

I see the issue in Textastic for iOS, but after filing a bug over there, they tell me they're also able to reproduce in Marked 2 (if MultiMarkdown is used but not if Discount is used)

[af4jm]

here's some Markdown to check if escapes are handled correctly (if the 2 lines render the same strings of characters, it passes, if the first line has extra backslashes, it fails)

\!\#\(\)\*\+\-\.\[\\\]\^\_\`\{\|\}\~\
``!#()*+-.[\]^_`{|}~``

[fletcher]

See if the latests commits in develop fix your results.

Thanks!