all: add import comments

Change-Id: I30a2b0dec44e3a41e06e418c3d7162da36b60510
Reviewed-on: https://go-review.googlesource.com/5710
Reviewed-by: Andrew Gerrand <adg@golang.org>

Author: adg

gotour/tour.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package main
+package main // import "golang.org/x/tour/gotour"
 
 import (
 	"bytes"

pic/pic.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package pic
+package pic // import "golang.org/x/tour/pic"
 
 import (
 	"bytes"

reader/validate.go

@@ -1,4 +1,8 @@
-package reader
+// Copyright 2014 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package reader // import "golang.org/x/tour/reader"
 
 import (
 	"fmt"

tree/tree.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package tree
+package tree // import "golang.org/x/tour/tree"
 
 import (
 	"fmt"

wc/wc.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package wc
+package wc // import "golang.org/x/tour/wc"
 
 import "fmt"