Forward magnum-ci build status to github

Running

1. Generate access token in github personal settings -> applications -> personal access tokens.
2. Copy config.example.yml to confi.yml, and fill access_token and repo name.
3. bundle
4. ./run.sh and then the server is up on port 4567, you need to config magnum notification settings (the path is /ci-forward-github) to make the whole thing working.

To config nginx front-end

location ~ ^/ci-forward-github/ {
  proxy_redirect off;
  proxy_pass http://localhost:4567;
}

To simply test the status

test_status=1 ./run.sh
curl localhost:4567/ci-forward-github/status