Implementing the CLI

$ ./app.py -h
usage: app.py [-h] [-p PORT] [-6] [-d] [-b DB_FILE]

Start a server to store location information.

optional arguments:
  -h, --help            show this help message and exit
  -p PORT, --port PORT  The port to run the web server on.
  -6, --ipv6            Listen to incoming connections via IPv6 instead of
                        IPv4.
  -d, --debug           Start in debug mode (with verbose HTTP error pages.
  -b DB_FILE, --db-file DB_FILE
                        The db to store the location information in.