Fix broken pipe error
- Make supervisored build_server as ruby git uses stdout
- Add logger to send log as websocket message
Add check method if working directory exists #12

- Remove useless constaint
- Fix typo
Replace WebSocket object to builder-logger

This fix make builder enable to log both in file and websocket object
Add error handling while building Docker image
Add function to confirm application in container is ready #13
Add ensure statement
Merge pull request #15 from mookjp/add-build-front

Add build front screen