Fix minor typos in comments (#486)

msg.go

@@ -29,8 +29,8 @@ const (
 var (
 	ErrAlg           error = &Error{err: "bad algorithm"}                  // ErrAlg indicates an error with the (DNSSEC) algorithm.
 	ErrAuth          error = &Error{err: "bad authentication"}             // ErrAuth indicates an error in the TSIG authentication.
-	ErrBuf           error = &Error{err: "buffer size too small"}          // ErrBuf indicates that the buffer used it too small for the message.
-	ErrConnEmpty     error = &Error{err: "conn has no connection"}         // ErrConnEmpty indicates a connection is being uses before it is initialized.
+	ErrBuf           error = &Error{err: "buffer size too small"}          // ErrBuf indicates that the buffer used is too small for the message.
+	ErrConnEmpty     error = &Error{err: "conn has no connection"}         // ErrConnEmpty indicates a connection is being used before it is initialized.
 	ErrExtendedRcode error = &Error{err: "bad extended rcode"}             // ErrExtendedRcode ...
 	ErrFqdn          error = &Error{err: "domain must be fully qualified"} // ErrFqdn indicates that a domain name does not have a closing dot.
 	ErrId            error = &Error{err: "id mismatch"}                    // ErrId indicates there is a mismatch with the message's ID.