move to s6 overlay structure (#13)

* move to s6 overlay structure

* Use alpine:latest and latest s6

* cleanup Dockerfile

* use .env file on docker run

* change mappings so all under one folder

* Update README

* change cron default to hourly to keep things updated

* add section about editing xteve settings

* add nice 'logging' to stdout

root/etc/services.d/xteve/run

@@ -0,0 +1,5 @@
+#!/usr/bin/with-contenv bash
+
+exec \
+	s6-setuidgid abc /bin/bash -c \
+	'xteve -port=$XTEVE_PORT -config=/xteve/'