Amalgamate outgoing messages.
Amalgamate outgoing messages.

Merge `accepts` and `learns` into one message with multiple `from` and
`to`. Do not include the value in the `accepted` message since it will
only ever be exchanged by the majority that will learn tha value from
the `accept` message.

Closes #101.

bigeasy/paxos,demarius/paxos,bigeasy/paxos,demarius/paxos