spec: add missing field to NodeInfoOther (#2426)

and fix formatting

Refs https://github.com/tendermint/tendermint/pull/2417#discussion_r218080500

docs/spec/p2p/peer.md

@@ -92,6 +92,7 @@ type NodeInfoOther struct {
 	ConsensusVersion string
 	RPCVersion       string
 	TxIndex          string
+	RPCAddress       string
 }
 ```
 

p2p/node_info.go

@@ -83,7 +83,8 @@ func (info NodeInfo) Validate() error {
 	// Sanitize versions
 	// XXX: Should we be more strict about version and address formats?
 	other := info.Other
-	versions := []string{other.AminoVersion,
+	versions := []string{
+		other.AminoVersion,
 		other.AminoVersion,
 		other.P2PVersion,
 		other.ConsensusVersion,