Fix a couple of comment typos.

spew/common_test.go

@@ -86,7 +86,7 @@ func (e customError) Error() string {
 }
 
 // stringizeWants converts a slice of wanted test output into a format suitable
-// for an test error message.
+// for a test error message.
 func stringizeWants(wants []string) string {
 	s := ""
 	for i, want := range wants {

spew/format.go

@@ -390,7 +390,7 @@ specifiers not handled by the custom formatter).
 
 Typically this function shouldn't be called directly.  It is much easier to make
 use of the custom formatter by calling one of the convenience functions such as
-Printf, Println, or Printf.
+Printf, Println, or Fprintf.
 */
 func NewFormatter(v interface{}) fmt.Formatter {
 	return newFormatter(&Config, v)