Add mailjet and sendgrid back in (#110)

Mostly a revert of 518d762fb001e230e5fbd2638bbaa45f77858c2d

Samples are needed for pages in the documentation.

compute/mailjet.js

@@ -0,0 +1,48 @@
+/**
+ * Copyright 2017, Google, Inc.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+'use strict';
+
+// [START send]
+var mailer = require('nodemailer');
+var smtp = require('nodemailer-smtp-transport');
+
+var transport = mailer.createTransport(
+  smtp({
+    host: 'in.mailjet.com',
+    port: 2525,
+    auth: {
+      user: process.env.MAILJET_API_KEY || '<your-mailjet-api-key',
+      pass: process.env.MAILJET_API_SECRET || '<your-mailjet-api-secret>',
+    },
+  })
+);
+
+transport.sendMail(
+  {
+    from: 'ANOTHER_EMAIL@ANOTHER_EXAMPLE.COM', // From address
+    to: 'EMAIL@EXAMPLE.COM', // To address
+    subject: 'test email from Node.js on Google Cloud Platform', // Subject
+    text: 'Hello!\n\nThis a test email from Node.js.', // Content
+  },
+  function(err, json) {
+    if (err) {
+      console.log(err);
+    } else {
+      console.log(json);
+    }
+  }
+);
+// [END send]