Riak 2.0 Feature: security

[kuenishi]

The PHP client needs to support security per basho/riak#355 .

• [ ] configure local credentials
• [ ] return appropriate errors when requests fail
• [ ] work correctly when requests succeed

php currently doesn't need "connect to protobuffs over TLS" because this only does support http.

[christophermancini]

Security is being released within the next few days as part of the rewrite.