Add "tls" extra to Twisted requirement
Add "tls" extra to Twisted requirement

This is required to install dependencies required for TLS support in
Twisted >= 15.1.0 (see
https://github.com/twisted/twisted/blob/twisted-15.1.0/NEWS).

google/certificate-transparency,RJPercival/certificate-transparency,pphaneuf/certificate-transparency,pphaneuf/certificate-transparency,RJPercival/certificate-transparency,google/certificate-transparency,pphaneuf/certificate-transparency,RJPercival/certificate-transparency,google/certificate-transparency,pphaneuf/certificate-transparency,RJPercival/certificate-transparency,google/certificate-transparency