feat(prototool): Add grpc-gateway protoc plugin (#66)

I also bumped prototool and protoc gen go plugin version to get version
supporting grpc-gateway generation.

prototool/Dockerfile

@@ -1,8 +1,9 @@
 FROM golang:1.11.0-alpine3.8 AS build
 
-ENV PROTOTOOL_VERSION=1.3.0
+ENV PROTOTOOL_VERSION=1.4.0
 ENV PROTOC_VERSION=3.6.1
-ENV PROTOC_GEN_GO_VERSION=1.2.0
+ENV PROTOC_GEN_GO_VERSION=1.3.1
+ENV PROTOC_GEN_GRPC_GATEWAY_VERSION=1.8.5
 
 RUN apk add --no-cache curl git libc6-compat
 
@@ -20,6 +21,11 @@ RUN go get github.com/golang/protobuf/... && \
   git checkout -b v$PROTOC_GEN_GO_VERSION && \
   go install ./protoc-gen-go
 
+RUN go get github.com/grpc-ecosystem/grpc-gateway/protoc-gen-grpc-gateway && \
+  cd /go/src/github.com/grpc-ecosystem/grpc-gateway && \
+  git checkout -b v$PROTOC_GEN_GRPC_GATEWAY_VERSION && \
+  go install ./protoc-gen-grpc-gateway
+
 FROM alpine:3.8
 
 LABEL vendor="Jobteaser" \
@@ -35,11 +41,13 @@ RUN apk add --no-cache libc6-compat git make ruby su-exec && \
 
 COPY --from=build /usr/local/bin/prototool /usr/local/bin/prototool
 COPY --from=build /go/bin/protoc-gen-go /usr/local/bin/protoc-gen-go
+COPY --from=build /go/bin/protoc-gen-grpc-gateway /usr/local/bin/protoc-gen-grpc-gateway
 
 ENV PATH /usr/local/go/bin:$PATH
 
 RUN chmod +x /usr/local/bin/prototool && \
-  chmod +x /usr/local/bin/protoc-gen-go
+  chmod +x /usr/local/bin/protoc-gen-go && \
+  chmod +x /usr/local/bin/protoc-gen-grpc-gateway
 
 COPY entrypoint.sh /usr/local/bin/entrypoint.sh
 RUN chmod +x /usr/local/bin/entrypoint.sh