@julian Just happened to me when I first registered, I logged out and back in and I was able to edit.
I felt like heroku was a bit of a pain in the ass to develop on (that's just me).
If you were just looking to mess about for a little while then you can google for a one month free coupon on digitalocean (no purchase necessary)
If you're sticking with heroku, have a look at our wiki for an installation guide:)
RE: Cant edit posts
RE: Anyone install with success on a shared host