Added a callback mechanism to chain adding.

Not sure if this is the right approach. Why? BlockChain shouldn't need
the "Ethereum" object. BlockChain shouldn't need to worry about
notifying listeners or message propagation.

peer.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"sync/atomic"
 	"time"
+
 	"github.com/ethereum/go-ethereum/chain/types"
 	"github.com/ethereum/go-ethereum/ethutil"
 	"github.com/ethereum/go-ethereum/logger"
@@ -23,7 +24,7 @@ const (
 	// The size of the output buffer for writing messages
 	outputBufferSize = 50
 	// Current protocol version
-	ProtocolVersion = 42
+	ProtocolVersion = 43
 	// Current P2P version
 	P2PVersion = 2
 	// Ethereum network version