Merge pull request #56 from mookjp/issue#55_make-uppercase-repo-name-to-downcase

#55 Modify docker-image prefix to downcase only as docker cant get uppercase characters
reverse_proxy requires r.uri as uri path
Merge pull request #59 from mookjp/issue-58-unparsed_uri

reverse_proxy requires r.uri as uri path
Fix to handle subdomain as git-commit-id inside pool

- Fix hook.rb and build_server so that it does not create
  another
  container if branch name is given.
- Fix Dockerfile to test builder gem while building
  the container
- Refactor hook.rb