Adding some features

main.js

@@ -1,3 +1,13 @@
-const Spotify = require('./src/spotify.js')
+const SpotifyController = require('./src/spotify.js')
 
-var spotifyController = new Spotify()
+var spotifyController = new SpotifyController().then(initializingSuccess, printError)
+
+// SpotifyController initialized
+function initializingSuccess(result) {
+    console.log(result)
+}
+
+// Print the error to the console
+function printError(error) {
+    console.log(error)
+}