Configurable input device

Version 2.0 adds the option to configure which input device is used.

💥 Breaking changes

• The command line interface now uses commands
  Add the command beat (e.g. aubio-beat-osc beat -c 127.0.0.1 1337 /foo) to get previous behaviour

🆕 New features

• Configurable input device
  Use -d DEVICE/--device DEVICE to set the input device to be used. If omitted, the system's default input is used
• Command to list input devices
  Run aubio-beat-osc list to print a list of all currently available input devices and their indices.