Appengine SDK for Go as a docker container

Quick and dirty work around for broken macOS sierra environment.

1. Install docker
2. docker build . -t appengine
3. docker run --rm -v $(pwd):/app -p 8000:8000 -p 8080:8080 -ti appengine
4. open http://localhost:8000