[spam][crazy] Adding Cert Pinning to E-X

[Undiscussed Horrific Abuse, One Victim of Many]

I'm thinking to start implementing what I came up with glancing
through, I'd first want to be able to query an aiorpcx socket for its
ssl fingerprint, which likely means getting the python socket from the
transport and reviewing its ssl attribute. Then I can reuse looking
that stuff up to implement the verification, too.