Allow passing in cowboy_protocol:opts()

 - Create 'start_listener/4' that accepts ProtoOpts for cowboy
 - Include default 'env' that is currently being set
Merge pull request #32 from ptuckey/cowboy-proto-opts

Allow passing in cowboy_protocol:opts()
Add mailing-list information to README.org
Fix mailing-list link
Merge pull request #1 from s1n4/master

Merge upstream changes from s1n4