Re-implement circusweb with tornadoweb

 - Drop gevent
 - Make circus ØMQ call asynchronous
 - Prepare implementation for multi-endpoint simultaneous connections (just need to update templates)
 - Implement multiuser for circusweb
 - Global flake8 compliancy
 - Remove legacy code
Merge pull request #19 from mozilla-services/tornado_rewriting

Re-implement circusweb with tornadoweb