Remove RC4 from libravatar-www

[François Marier]

We should move away from RC4 on libravatar-www given that it's not all that great anymore:

  http://blog.cryptographyengineering.com/2013/03/attack-of-week-rc4-is-kind-of-broken-in.html

There's probably no need to change -seccdn though.

[François Marier (fmarier)]

Now that the main server is on wheezy, we should improve its TLS config:

  http://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/

Removing RC4, disabling compression and favouring the TLS 1.2 ciphers that give perfect forward secrecy.