* p2p/conn: simplify secret connection handshake malleability fix with merlin
Introduces new dependencies on github.com/gtank/merlin and sha3 as a cryptographic primitive
This also only uses the transcript hash as a MAC.
* p2p/conn: avoid string to byte conversion
https://github.com/uber-go/guide/blob/master/style.md#avoid-string-to-byte-conversion