This drops support for the TCP port and switches to using a socket at
/var/run/weldr/api.socket
Also add the start of some docs for lorax-composer.
--host and --port argument have been removed.
--group sets the group name to use for access to the socket and its
parent directory. Defaults to 'weldr'
--socket sets the full path to the socket to create. Defaults to
'/var/run/weldr/api.socket'
