refactor: use alias package punycode.js

[SukkaW]

punycode package uses the same name as the inbuilt punycode package in node.js. Related report can be found here.

And I have found the package punycode.js on npm. It is exact the same package as punycode and has the same maintainer, which could act as an alias to punycode. The only difference between them is punycode package has added es6 module support in [email protected].

[coveralls]

Coverage increased (+1.4%) to 96.647% when pulling 4af01e7 on SukkaW:deps-punycode into ea43fba on hexojs:master.

[curbengh]

whatwg has built-in punycode support, but it's not used here yet due to a bug in Node 8. Once Node 8 EOL (in a month), punycode shall be dropped.

hexo-util/lib/encode_url.js

Lines 23 to 24 in ea43fba

	// TODO: refactor to url.format() once Node 8 EOL
	return parsed.toString().replace(parsed.hostname, toUnicode(parsed.hostname));