Use net.Buffers to write multiple slices to connection

Closes #346.

conn.go

@@ -370,7 +370,7 @@ func (c *Conn) writeFatal(err error) error {
 	return err
 }
 
-func (c *Conn) write(frameType int, deadline time.Time, bufs ...[]byte) error {
+func (c *Conn) write(frameType int, deadline time.Time, buf0, buf1 []byte) error {
 	<-c.mu
 	defer func() { c.mu <- true }()
 
@@ -382,15 +382,14 @@ func (c *Conn) write(frameType int, deadline time.Time, bufs ...[]byte) error {
 	}
 
 	c.conn.SetWriteDeadline(deadline)
-	for _, buf := range bufs {
-		if len(buf) > 0 {
-			_, err := c.conn.Write(buf)
+	if len(buf1) == 0 {
+		_, err = c.conn.Write(buf0)
+	} else {
+		err = c.writeBufs(buf0, buf1)
+	}
 	if err != nil {
 		return c.writeFatal(err)
 	}
-		}
-	}
-
 	if frameType == CloseMessage {
 		c.writeFatal(ErrCloseSent)
 	}

conn_write.go

@@ -0,0 +1,15 @@
+// Copyright 2016 The Gorilla WebSocket Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build go1.8
+
+package websocket
+
+import "net"
+
+func (c *Conn) writeBufs(bufs ...[]byte) error {
+	b := net.Buffers(bufs)
+	_, err := b.WriteTo(c.conn)
+	return err
+}

conn_write_legacy.go

@@ -0,0 +1,18 @@
+// Copyright 2016 The Gorilla WebSocket Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !go1.8
+
+package websocket
+
+func (c *Conn) writeBufs(bufs ...[]byte) error {
+	for _, buf := range bufs {
+		if len(buf) > 0 {
+			if _, err := c.conn.Write(buf); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}