I’ve got exactly the same problem, and have been following the same tutorial. docker info provides the same information that @Fabian has mentioned.
I’m running the suggested build of Ubuntu and can confirm that I’m on a 64bit version of it. I’m not really experienced with Linux but I couldn’t see any anything that looked like an error during the install of docker. The only thing that I’m aware that I did do which was off script was to add myself to the docker group as per the installer suggestions using:
sudo usermod -aG docker {USERNAME}