Homebrew compatibility

This release makes the project compatible with homebrew's policy

1.1.0 - Improve user experience

This new release fixes 2 user experience issues :

• #6 support multiple external keyboards without serial numbers
  This is fixed by introducing a -l or --location parameter to program startup which includes the keyboards locationId in the keyboard identifier used for the mapping.
  This will effectively associate the input source with a specific keyboard plugged on a specific usb port. Moving the same keyboard to a different USB port will result in a new keyboard id and mapping being registered.
  A repeatable -v flag has also been introduced to help in troubleshooting for future issues.

• #5 Save settings on restart
  The state of keyboard mappings is now saved to UserDefaults and reloaded on restart. This is especially useful after a reboot.

1.0.0

This software memorizes the last active osx input source for a given keyboard and restores it automatically when that keyboard becomes the active keyboard.