do not build on alpine

testing this without alpine because alpine bug might be
 causing issue where redis does not resolve new ip address:
 gliderlabs/docker-alpine#255

* also pin to 4.0

Dockerfile

@@ -1,6 +1,5 @@
-FROM redis:4-alpine
+FROM redis:4.0
 ENTRYPOINT ["/app/redis-or-bootstrap"]
-RUN apk --update --no-cache add bash
 
 COPY redis-or-bootstrap /app/redis-or-bootstrap
 USER guest