Clarify ngrok/http post arrangement

[charlesreid1]

This is intended as an example for beginners, but assumes a lot of understanding from the network side. Take this for example:

Tunneling Using ngrok you can port a public url to your local server.

You link to ngrok, but don't explain anything about how it works or what it's doing. As an ngrok user I had no trouble understanding that, but you can't just assume everyone knows or can get up to speed on what ngrok is - particularly in a beginners' tutorial.

If you want to improve your tutorial (and you should, see #1), this would be a great place to start.