Install script should check for existing installation and perform an update
Indie Web Server is already installed and the install script is run.
The install script should check for an existing installation. If one exists, it should ask it for its version and compare that to its own version. If the latest version is already installed, the install script should let the person know that and exit. If it is not, it should continue with the installation, informing the person that they are upgrading from older version to latest version.