Installs a container
An Installer is meant to install a container on your local machine. There is currently only a single Installer implementation:
ZipURLInstaller which downloads a zipped container distribution from a URL and which installs it (i.e. unpacks it) in a specified directory. This is useful if you wish to fully automate a container installation without having to ask the user to manually install a container on their machine.
Of course you don't need to use an Installer and you can rely on the fact that whoever is using Cargo already has a container installed on his machine.