Update punycode.js

[kurtextrem]

From v1.2.4 to v1.3.1 (only v1.3 in between)
Not sure if it's worth upgrading though. The new version(s) introduce email "parsing"(?) and could be potential performance decrease.

[gorhill]

I don't think it's worth it. The only use for punycode.js is to parse Mozilla's Public Suffix List, which is just domain name stuff. I could maybe use it to render the domain and host names in the request log, but still, nothing related to email. I rather not change external libraries until there is a tangible benefit for the project.