Use a multi-stage Dockerfile

Previously, we needed a script to build a minimal docker image without build
dependency.

Docker's new multi-stage builds allow us to specify all of this logic in the
Dockerfile, eliminating the need for the _dockerize_ script.

Fixes #43

Dockerfile

@@ -1,5 +1,10 @@
-FROM debian:jessie-slim
-
-COPY ./target/x86_64-unknown-linux-gnu/release/linkerd-tcp /usr/local/bin/
+FROM linkerd/rustup-nightly:v1
+RUN rustup update nightly
+RUN mkdir -p /linkerd-tcp
+COPY . /linkerd-tcp
+WORKDIR /linkerd-tcp
+RUN cargo build --release
 
+FROM debian:jessie-slim
+COPY --from=0 /linkerd-tcp/target/x86_64-unknown-linux-gnu/release/linkerd-tcp /usr/local/bin/
 ENTRYPOINT ["/usr/local/bin/linkerd-tcp"]

README.md

@@ -92,7 +92,7 @@ debugging, set `RUST_LOG=trace`.
 To build the linkerd/linkerd-tcp docker image, run:
 
 ```bash
-./dockerize latest
+docker build -t linkerd/linkerd-tcp:latest .
 ```
 
 Replace `latest` with the version that you want to build.