crypto/md5,sha1: add examples for Sum

LGTM=dave
R=golang-codereviews, dave
CC=golang-codereviews
https://golang.org/cl/66900044

src/pkg/crypto/md5/example_test.go

@@ -17,3 +17,9 @@ func ExampleNew() {
 	fmt.Printf("%x", h.Sum(nil))
 	// Output: e2c569be17396eca2a2e3c11578123ed
 }
+
+func ExampleSum() {
+	data := []byte("These pretzels are making me thirsty.")
+	fmt.Printf("%x", md5.Sum(data))
+	// Output: b0804ec967f48520697662a204f5fe72
+}

src/pkg/crypto/sha1/example_test.go

@@ -12,7 +12,14 @@ import (
 
 func ExampleNew() {
 	h := sha1.New()
-	io.WriteString(h, "His money is twice tainted: 'taint yours and 'taint mine.")
+	io.WriteString(h, "His money is twice tainted:")
+	io.WriteString(h, " 'taint yours and 'taint mine.")
 	fmt.Printf("% x", h.Sum(nil))
 	// Output: 59 7f 6a 54 00 10 f9 4c 15 d7 18 06 a9 9a 2c 87 10 e7 47 bd
 }
+
+func ExampleSum() {
+	data := []byte("This page intentionally left blank.")
+	fmt.Printf("% x", sha1.Sum(data))
+	// Output: af 06 49 23 bb f2 30 15 96 aa c4 c2 73 ba 32 17 8e bc 4a 96
+}