cmd/tendermint/commands/lite: add tcp scheme to address URLs (#1297)

Noticed while investigating
https://github.com/tendermint/tendermint/issues/970

As reported by @zramsay, we'd get the warning
from tendermint/rpc/lib because we were passing in
scheme-less addresses, so by default use "tcp".

Also by default, "node" (nodeAddr) has been set to:
  "tcp://localhost:46657"
instead of the bare:
  "localhost:46657"

This change is just to clean up such warnings as
they spuriously would spook users for a package "lite"
that claims to be secure.

cmd/tendermint/commands/lite.go

@@ -1,6 +1,9 @@
 package commands
 
 import (
+	"fmt"
+	"net/url"
+
 	"github.com/spf13/cobra"
 
 	cmn "github.com/tendermint/tmlibs/common"
@@ -32,12 +35,36 @@ var (
 
 func init() {
 	LiteCmd.Flags().StringVar(&listenAddr, "laddr", ":8888", "Serve the proxy on the given port")
-	LiteCmd.Flags().StringVar(&nodeAddr, "node", "localhost:46657", "Connect to a Tendermint node at this address")
+	LiteCmd.Flags().StringVar(&nodeAddr, "node", "tcp://localhost:46657", "Connect to a Tendermint node at this address")
 	LiteCmd.Flags().StringVar(&chainID, "chain-id", "tendermint", "Specify the Tendermint chain ID")
 	LiteCmd.Flags().StringVar(&home, "home-dir", ".tendermint-lite", "Specify the home directory")
 }
 
+func ensureAddrHasSchemeOrDefaultToTCP(addr string) (string, error) {
+	u, err := url.Parse(nodeAddr)
+	if err != nil {
+		return "", err
+	}
+	switch u.Scheme {
+	case "tcp", "unix":
+	case "":
+		u.Scheme = "tcp"
+	default:
+		return "", fmt.Errorf("unknown scheme %q, use either tcp or unix", u.Scheme)
+	}
+	return u.String(), nil
+}
+
 func runProxy(cmd *cobra.Command, args []string) error {
+	nodeAddr, err := ensureAddrHasSchemeOrDefaultToTCP(nodeAddr)
+	if err != nil {
+		return err
+	}
+	listenAddr, err := ensureAddrHasSchemeOrDefaultToTCP(listenAddr)
+	if err != nil {
+		return err
+	}
+
 	// First, connect a client
 	node := rpcclient.NewHTTP(nodeAddr, "/websocket")