Use multi-stage docker build

Dockerfile

@@ -1,2 +1,13 @@
-FROM golang:onbuild
-COPY config_example.json config.json
+FROM golang:1.9.4 as build
+WORKDIR /go/src/github.com/thrasher-/gocryptotrader
+COPY . .
+RUN mv -vn config_example.json config.json \
+ && go get -v -d \
+ && GOARCH=386 GOOS=linux CGO_ENABLED=0 go install -v \
+ && mv /go/bin/linux_386 /go/bin/gocryptotrader
+
+FROM alpine:latest
+COPY --from=build /go/bin/gocryptotrader /app/
+COPY --from=build /go/src/github.com/thrasher-/gocryptotrader/config.json /app/
+EXPOSE 9050
+CMD ["/app/gocryptotrader"]