added auto backup

Dockerfile

@@ -1,9 +1,13 @@
-FROM alpine:3.6
+# use edge image for higher client versions
+FROM alpine:edge
+
 MAINTAINER Benjamin Böhmke <benjamin@boehmke.net>
 
-RUN apk add --no-cache mysql-client postgresql-client postgresql-bdr
+RUN apk add --no-cache mysql-client postgresql-client
 
 ADD entrypoint.sh /entrypoint.sh
 
+VOLUME /backup/
+
 ENTRYPOINT ["/entrypoint.sh"]
 CMD ["app:init"]