Error deploying Alexa Skill to heroku

I appreciate the simplicity with which the jovo-framework developers are explaining their tutorials.
Having finished building my skill, using this great framework, I am now trying to deploy it on Heroku. I followed this tutorial:
How to Deploy your Alexa Skill and Google Action to Heroku

I believe I have done all the necessary steps as demanded. But when I run this in the console:

heroku open  

the app doesn't work and I get these errors on the console:

I am really looking forward to publish my skill and finally see the fruits of my work.
So if anyone knows what might be causing this error, I would totally appreciate the help. Thanks.

The npm start script needs to do node index.js --webhook instead of node index.js.

The old one was pre Jovo v1.0, forgot to change this in one part of the tutorial. Updated now: How to Deploy your Alexa Skill and Google Action to Heroku > Updating the Package.json.