Docker instructions and configuration (#33)

* Added dockerfile

* Docker configuration

* Added Docker images, composer configuration and documentation

Dockerfile

@@ -0,0 +1,20 @@
+FROM golang:1.9.2-alpine AS builder
+LABEL maintainer="joona@kuori.org"
+
+RUN apk add --update gcc musl-dev git
+
+RUN go get github.com/joohoi/acme-dns
+WORKDIR /go/src/github.com/joohoi/acme-dns
+RUN CGO_ENABLED=1 go build
+
+FROM alpine:latest
+
+WORKDIR /root/
+COPY --from=builder /go/src/github.com/joohoi/acme-dns .
+RUN mkdir -p /etc/acme-dns
+RUN mkdir -p /var/lib/acme-dns
+RUN rm -rf ./config.cfg
+
+VOLUME ["/etc/acme-dns", "/var/lib/acme-dns"]
+ENTRYPOINT ["./acme-dns"]
+EXPOSE 53 80 443