make User-Agent RFC1945 compliant

This is the product name without the optional '/' + version.
The parens are a comment, the '+' preceding the URL is common practice

https://tools.ietf.org/html/rfc1945#section-10.15

lib/networking.js

@@ -38,7 +38,7 @@ exp.get_from_options = function(rid, url, options, callback) {
   request.get({
     url: url,
     headers: {
-      "User-Agent": "https://crafatar.com"
+      "User-Agent": "Crafatar (+https://crafatar.com)"
     },
     timeout: config.server.http_timeout,
     followRedirect: false,