Connection values (such as redis server port and the port to run farside
on) as well as the services json file to use can now be set via
environment variables:
FARSIDE_PORT sets the port for Farside to run on
FARSIDE_REDIS_PORT sets the redis server port for Farside to use
FARSIDE_SERVICES_JSON sets the services json file for Farside to use
This partially addresses the move towards de-listing Cloudflare
instances by default by allowing different services json files to be
used with different redis servers.
See #43