fix: Do not attempt to use url.URL when unavailable

Fix #61

This should not be ported to the latest branch, as Node.js v6 support
was dropped there anyway.

index.js

@@ -108,7 +108,9 @@ function parseGitUrl (giturl) {
   var matched = giturl.match(/^([^@]+)@([^:/]+):[/]?((?:[^/]+[/])?[^/]+?)(?:[.]git)?(#.*)?$/)
   if (!matched) {
     var legacy = url.parse(giturl)
-    if (legacy.auth) {
+    // If we don't have url.URL, then sorry, this is just not fixable.
+    // This affects Node <= 6.12.
+    if (legacy.auth && typeof url.URL === 'function') {
       // git urls can be in the form of scp-style/ssh-connect strings, like
       // git+ssh://user@host.com:some/path, which the legacy url parser
       // supports, but WhatWG url.URL class does not.  However, the legacy

test/auth.js

@@ -16,3 +16,9 @@ tap.equal(parsedUrl.hostname, 'github.com')
 // For full backwards-compatibility; support auth where only username or only password is provided
 tap.equal(HostedGitInfo.fromUrl('https://user%3An%40me@github.com/npm/hosted-git-info.git').auth, 'user%3An%40me')
 tap.equal(HostedGitInfo.fromUrl('https://:p%40ss%3Aword@github.com/npm/hosted-git-info.git').auth, ':p%40ss%3Aword')
+
+// don't try to url.URL parse it if url.URL is not available
+// ie, node <6.13.  This is broken, but at least it doesn't throw.
+url.URL = null
+var parsedInfo = HostedGitInfo.fromUrl('https://user%3An%40me:p%40ss%3Aword@github.com/npm/xyz.git')
+tap.equal(parsedInfo.auth, 'user:n@me:p@ss:word')