Add l2 implementation

Dockerfile.l2

@@ -0,0 +1,30 @@
+FROM golang:1.8
+
+# Copy the runtime dockerfile into the context as Dockerfile
+COPY . /go/src/github.com/play-with-docker/play-with-docker
+
+WORKDIR /go/src/github.com/play-with-docker/play-with-docker
+
+RUN go get -v -d ./...
+
+RUN ssh-keygen -N "" -t rsa -f /etc/ssh/ssh_host_rsa_key >/dev/null
+
+WORKDIR /go/src/github.com/play-with-docker/play-with-docker/router/l2
+
+RUN CGO_ENABLED=0 go build -a -installsuffix nocgo -o /go/bin/play-with-docker-l2 .
+
+
+FROM alpine
+
+RUN apk --update add ca-certificates
+RUN mkdir /app
+
+COPY --from=0 /go/bin/play-with-docker-l2 /app/play-with-docker-l2
+COPY --from=0 /etc/ssh/ssh_host_rsa_key /etc/ssh/ssh_host_rsa_key
+
+WORKDIR /app
+CMD ["./play-with-docker-l2", "-ssh_key_path", "/etc/ssh/ssh_host_rsa_key"]
+
+EXPOSE 22
+EXPOSE 53
+EXPOSE 443