examples: Add webhook example for Heroku (#271)

examples/herokuWebHook.js

@@ -0,0 +1,36 @@
+/**
+ * This example demonstrates setting up webhook
+ * on the Heroku platform.
+ */
+
+
+const TOKEN = process.env.TELEGRAM_TOKEN || 'YOUR_TELEGRAM_BOT_TOKEN';
+const TelegramBot = require('..');
+
+const options = {
+  webHook: {
+    //Port which you should bind to is assigned to $PORT variable
+    //See: https://devcenter.heroku.com/articles/dynos#local-environment-variables
+    port: process.env.PORT
+    // you do NOT need to set up certificates since Heroku provides
+    // the SSL certs already (https://<app-name>.herokuapp.com)
+    // Also no need to pass IP because on Heroku you need to bind to 0.0.0.0
+  }
+};
+// Heroku routes from port :443 to $PORT
+// Add URL of your app to env variable or enable Dyno Metadata
+// to get this automatically
+// See: https://devcenter.heroku.com/articles/dyno-metadata
+const url = process.env.APP_URL || 'https://<app-name>.herokuapp.com:443';
+const bot = new TelegramBot(TOKEN, options);
+
+
+// This informs the Telegram servers of the new webhook.
+// Note: we do not need to pass in the cert, as it already provided
+bot.setWebHook(`${url}/bot${TOKEN}`);
+
+
+// Just to ping!
+bot.on('message', function onMessage(msg) {
+  bot.sendMessage(msg.chat.id, 'Running on Heroku!');
+});