Add a --help option

[fryfrog]

It'd be really awesome if you could run the script w/ a --help option instead of having it barf because the config file isn't found.

$ python /usr/lib/radarrsync/RadarrSync.py --help
Traceback (most recent call last):
  File "/usr/lib/radarrsync/RadarrSync.py", line 215, in <module>
    radarrServer['url'] = ConfigSectionMap("Radarr")['url']
  File "/usr/lib/radarrsync/RadarrSync.py", line 19, in ConfigSectionMap
    options = Config.options(section)
  File "/usr/lib/python3.7/configparser.py", line 674, in options
    raise NoSectionError(section) from None
configparser.NoSectionError: No section: 'Radarr'