Disable insecure ciphers

[JoeChapman]

A recent ITHC report for a service using docker-nginx-proxy v2.0.2.0 has said that some ciphers supported by the web server is not sufficiently cryptographically
secure. And that the ciphers cannot guarantee protection from brute-force decryption
should the traffic be captured.

It goes on to suggest we disable all ciphers that use a key length of less than 128 bits.

It cites https://wiki.mozilla.org/Security/Server_Side_TLS#Recommended_configurations as a reference