add back getCert

lib/client.js

@@ -10,5 +10,8 @@
 exports.Acme = require('acme-client');
 exports.registerNewAccount = require('register-new-account');
 exports.getCertificate = require('get-certificate');
-exports.getCert=function (options) {
+exports.getCert=function (options, cb) {
+  exports.registerNewAccount(options, function () {
+    exports.getCertificate(options, cb);
+  });
 };