fixed static string example that would not display MOTD on CentOS

Hi,

The example given in the README for providing a static string as the MOTD did not work without adding a newline character (`\n`) at the end .

Perhaps you could do something within the `init.pp` to ensure a newline is inserted at the end (HTH) but at least the README example will now work.

This was tested on CentOS `6.5` using Puppet `3.6.2`.