Fix order of revocation command.

According to 'man gpg' the order of arguments should be

gpg [--homedir name] [--options file] [options] command [args]

In this case '--gen-revoke' is the command, '$KEYID' is an argument and
'--output $GNUPGHOME/revoke.asc' is an option. Previously this was
incorrect (option came first) and would spawn an error.

README.md

@@ -881,7 +881,7 @@ Even worse, we cannot advertise this fact in any way to those that are using our
 To create the revocation certificate:
 
 ``` console
-$ gpg --gen-revoke $KEYID --output $GNUPGHOME/revoke.asc
+$ gpg --output $GNUPGHOME/revoke.asc --gen-revoke $KEYID
 ```
 
 The `revoke.asc` certificate file should be stored (or printed) in a (secondary) place that allows retrieval in case the main backup fails.