Add tornado backend.
tornado.netutil.bind_unix_socket() removes existing socket.
fix flake8
Fix test_server
Fix travis and tox
Fix potensial attribute error.
Support Tornado's TCPServer and web.Application.
Fix bug.
Add example for tornado.
Fix flake8 error.
Fix gevent monkey patch is applied for non gevent servers.
Fix tests.
Show Python version before running test.
Wait for server starts.
Install coverage befor running coveralls
Remove coverage from tests_require.

It puts egg file to current directory.
The egg prevents `pip install coverage`
Merge pull request #61 from methane/tornado

Add tornado backend.