Optimize CI with travis

* Use container-based infrastructure of Travis
* Avoid building protoc every time
* Avoid building `go tool vet`

.travis.build-protoc.sh

@@ -0,0 +1,21 @@
+#!/bin/sh -eu
+protoc_version=$1
+if test -z "${protoc_version}"; then
+	echo "Usage: .travis.build-protoc.sh protoc-version"
+	exit 1
+fi
+if ! $HOME/local/bin/protoc-${protoc_version} --version 2>/dev/null; then
+	rm -rf $HOME/local
+
+	wget https://github.com/google/protobuf/archive/v${protoc_version}.tar.gz
+	tar xvzf v${protoc_version}.tar.gz
+	cd protobuf-${protoc_version}
+	./autogen.sh
+	./configure --prefix=$HOME/local --program-suffix=-${protoc_version}
+	make -j 4
+	make install
+fi
+ln -sf $HOME/local/bin/protoc-${protoc_version} $HOME/local/bin/protoc
+
+echo \$ $HOME/local/bin/protoc --version
+$HOME/local/bin/protoc --version

.travis.yml

@@ -1,26 +1,29 @@
+branches:
+  only:
+    - master
 language: go
-
+sudo: false
 go:
 - 1.3
 - tip
+cache:
+  directories:
+  - $HOME/local
 before_install:
-- cd /tmp
-- wget https://github.com/google/protobuf/archive/v3.0.0-alpha-2.tar.gz
-- tar xvzf v3.0.0-alpha-2.tar.gz
-- cd protobuf-3.0.0-alpha-2
-- ./autogen.sh
-- ./configure
-- make
-- sudo make install
+- ./.travis.build-protoc.sh 3.0.0-alpha-2
 - go get github.com/golang/lint/golint
-- go get golang.org/x/tools/cmd/vet
 install:
 - go get github.com/gengo/grpc-gateway/protoc-gen-grpc-gateway
 script:
 - make examples
 - test -z "$(git -C $GOPATH/src/github.com/gengo/grpc-gateway status --porcelain)"
 - go test -v github.com/gengo/grpc-gateway/protoc-gen-grpc-gateway/... --logtostderr
-- golint github.com/gengo/grpc-gateway/protoc-gen-grpc-gateway
-- golint github.com/gengo/grpc-gateway/runtime
-- go tool vet $GOPATH/src/github.com/gengo/grpc-gateway/protoc-gen-grpc-gateway
-- go tool vet $GOPATH/src/github.com/gengo/grpc-gateway/runtime
+- golint github.com/gengo/grpc-gateway/protoc-gen-grpc-gateway/...
+- golint github.com/gengo/grpc-gateway/runtime/...
+- golint github.com/gengo/grpc-gateway/utilities/...
+- go vet github.com/gengo/grpc-gateway/protoc-gen-grpc-gateway/...
+- go vet github.com/gengo/grpc-gateway/runtime/...
+- go vet github.com/gengo/grpc-gateway/utilities/...
+env:
+  global:
+  - "PATH=$PATH:$HOME/local/bin"