1.1.0

• Add henson.cli.register_commands to extend the command line interface
• Messages are logged using logging.DEBUG instead of logging.INFO
• Calls to print in henson.cli.run are updated to app.logger.info
• References to objects used by henson.Application are removed once they
  are no longer needed to allow the memory to be freed up before the next
  message is received.
• uvloop_ will be used for the event loop if it's installed.
• Automatically register extensions to a registry on the application
• Add hensoncli Sphinx directive to document extensions to the command line
  interface
• henson.cli.run and any command line extensions that request it support
  quiet and verbose flags to set verbosity