Add Vagrantfile for trying out in a local VM

[peterdemin]

I had to extract the SSH key configuration from the installation script and put it into a follow-up instruction.
You need to have Vagrant and VirtualBox installed.
The usage is:

1. Run vagrant up
2. Copy-paste and run commands from the output.
3. Use sailor as a target host.
4. Use uWSGI without SSL, because the VM is not accessible from the internet and can't have Let'sEncrypt access: server_name: _, server_port: NNNN