Ensure apt-transport-https is installed.

Without this, APT doesn't know what to do with Docker's HTTPS APT
repository.
Pull the repo key over HTTPS
Merge pull request #11 from psi/apt-transport-https

Handle Docker's HTTPS apt repository
Use HTTPS for Apt repository
Clean up bind_uri text
Merge pull request #12 from rgbkrk/patch-1

Clean up bind_uri text
Merge branch 'master' into ports
Only set port when specified