Ref: tendermint/tmkms#57

An IPC channel (UNIX socket) between KMS and a tendermint validator node should serve the use case where validators deploy the KMS next to a validator node on the same host.

This could allow for a connection with less overhead complexity thereby increasing reliability.

I could take care of the issue and in the course of this also fix the SecureConnection implementation which is currently broken.

Since the underlying TCP socket is already built in (and can be shared with SecureConnection) I will not need to introduce a lot of unnecessary overhead.