consensus: link to spec from readme (#1609)

consensus/README.md

@@ -1,18 +1 @@
-# The core consensus algorithm.
-
-* state.go - The state machine as detailed in the whitepaper
-* reactor.go - A reactor that connects the state machine to the gossip network
-
-# Go-routine summary
-
-The reactor runs 2 go-routines for each added peer: gossipDataRoutine and gossipVotesRoutine.
-
-The consensus state runs two persistent go-routines: timeoutRoutine and receiveRoutine.
-Go-routines are also started to trigger timeouts and to avoid blocking when the internalMsgQueue is really backed up.
-
-# Replay/WAL
-
-A write-ahead log is used to record all messages processed by the receiveRoutine,
-which amounts to all inputs to the consensus state machine:
-messages from peers, messages from ourselves, and timeouts.
-They can be played back deterministically at startup or using the replay console. 
+See the [consensus spec](https://github.com/tendermint/tendermint/tree/master/docs/spec/consensus)