Merge pull request #70 from shin-/master

Fixed simple checksum
Added sample nginx.conf to contrib
Merge branch 'master' of https://github.com/dotcloud/docker-registry
Added support for travis-ci + tox
Merge branch 'master' of github.com:dotcloud/docker-registry
Update README.md
Fix travis-ci
Merge branch 'master' of github.com:dotcloud/docker-registry
Update README.md
Added support for flake8 checks with hacking package enabled
Merge branch 'master' of github.com:dotcloud/docker-registry
Fix test-requirements conflicts
Fix test-requirements conflicts
Update README.md
Add ability to set env var in config value
Implemented optional caching over Redis
Redis can be enabled if cache is True
Added redis requirement
Fixed unittests
Fixed cache