Add a version number in the "gorgon/app" package
Add a "dist" target to the Makefile

The purpose of the `dist` target is to build an archive that can be used
to install Gorgon.
Get config file from cmd line argument

The path to the configuration file can be provided at runtime with the
`-c` command line argument. The default path is `gorgon.ini`.
Update README.rst