use correct version in UA

lib/node/client-user-agent.js

@@ -1,6 +1,7 @@
 'use strict';
 
 var os = require('os');
+var ver = require('../../package.json');
 
 var UserAgent = module.exports;
 UserAgent.get = function(me) {
@@ -12,7 +13,9 @@ UserAgent.get = function(me) {
 	// And https://community.letsencrypt.org/t/user-agent-flag-explained/3843/2
 
 	var ua =
-		'ACME.js/v3 ' +
+		'ACME.js/' +
+		ver +
+		' ' +
 		process.release.name +
 		'/' +
 		process.version +