Add docker stuff

.dockerignore

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+target

Dockerfile

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+FROM alpine:3.9 AS builder
+RUN apk add --no-cache rust cargo openssl-dev
+WORKDIR /usr/src/crepo
+COPY Cargo.* ./
+COPY src ./src
+RUN cargo build --release
+
+FROM alpine:3.9
+RUN apk add --no-cache libgcc openssl
+COPY --from=builder /usr/src/crepo/target/release/crepo /usr/bin/
+CMD ["crepo"]