Deprecate msfpayload and msfencode

See #4326, but it does not close it.

When you use msfencode, it will print the following message:

```
[!] ************************************************************************
[!] *               The utility msfencode is deprecated!                   *
[!] *              It will be removed on or about 2015-06-08               *
[!] *                   Please use msfvenom instead                        *
[!] ************************************************************************
```

For msfpayload:

```
[!] ************************************************************************
[!] *               The utility msfpayload is deprecated!                  *
[!] *              It will be removed on or about 2015-06-08               *
[!] *                   Please use msfvenom instead                        *
[!] ************************************************************************
```

But both remain functional.

Please make sure Travis is green.