vendor: update all dependencies except Azure SDK

The Azure SDK doesn't support Go 1.5 anymore. We can't upgrade it until
Go 1.8 comes out.

vendor/github.com/nsf/termbox-go/termbox.go

@@ -233,10 +233,7 @@ func send_char(x, y int, ch rune) {
 func flush() error {
 	_, err := io.Copy(out, &outbuf)
 	outbuf.Reset()
-	if err != nil {
-		return err
-	}
-	return nil
+	return err
 }
 
 func send_clear() error {