Configure Travis CI with browser integration test

.travis.yml

@@ -9,21 +9,26 @@ go:
 cache:
   directories:
   - $HOME/local
+  - ${TRAVIS_BUILD_DIR}/examples/browser/node_modules
 before_install:
 - ./.travis/build-protoc.sh 3.0.0-beta-3
 - ./.travis/install-swagger-codegen.sh 2.1.6
+- nvm install v6.1 && nvm use v6.1 && node --version
 - go get github.com/golang/lint/golint
 - go get github.com/dghubble/sling
 install:
 - go get github.com/gengo/grpc-gateway/protoc-gen-grpc-gateway
 - go get github.com/gengo/grpc-gateway/runtime
 - go get github.com/gengo/grpc-gateway/examples
 - go get github.com/gengo/grpc-gateway/examples/server
+before_script:
+- sh -c 'cd examples/browser && npm install'
 script:
 - make realclean && make examples SWAGGER_CODEGEN="java -jar $HOME/local/swagger-codegen-cli.jar"
 - if ! go version | grep devel; then test -z "$(git status --porcelain)" || (git status; git diff; exit 1); fi
 - env GLOG_logtostderr=1 go test -race -v github.com/gengo/grpc-gateway/...
 - make lint
+- sh -c 'cd examples/browser && gulp'
 env:
   global:
   - "PATH=$PATH:$HOME/local/bin"