Display list of available instances on home page

This introduces a number of new changes:
- Services are now inserted into redis with a prefix prepended to the
key name. This allows for easier filtering to get only live instances.
- The home page now uses an eex template for displaying all live
instances for every service, determined by the last update
- A "last_updated" field was added
- farside.ex was added to contain all functionality related to querying
for instances (WIP)
- Other improvements

config/config.exs

@@ -4,4 +4,6 @@ config :farside,
   redis_conn: "redis://localhost:6379",
   fallback_str: "-fallback",
   update_file: ".update-results",
-  services_json: "services.json"
+  service_prefix: "service-",
+  services_json: "services.json",
+  index: "index.eex"