Adding part of client.pp code into new class
backupninja::client::defaults in an attempt to avoid duplicate
definitions inside backupninja::client::key.

* update the README to be more clear about how this works, provide
more examples and included details about the addition of the
backupninja::client::duplicity class

fix rdiff-backup class name, "You can use Aa-Zz, 0-9 and underscores in variables, resources and class names." which means no dashes in class names either

remove redundant case statements which tested to see if the package ensure version variables were set
changed the $rdiff-backup_ensure_version variable to $rdiff_backup_ensure_version as dashes are not allowed in variable names

create subclasses for maildir and rdiff-backup. If you are using these features of backupninja, you'll want to switch to doing "include backupninja::client::maildir" for the machines that need it and this will pull in backupninja::client, so you don't need to include that anymore if you were explicitly doing so for those machines (although it shouldn't hurt). Right now what using these new subclasses will get you is dependencies on needed packages, but in the future there might be more.

when you have two rdiff-backup calls, then the User is a Duplicate
definition, i think the only way to do it is to have a variable that
you can set to turn off user handling (which we make $installuser and
$usermanage be consistant with $installkey and $keymanage), which is
set true by default, but when you have a second rdiff call on a host,
you can set it to false

change the $host variable to no longer use the $user variable, that way
multiple rdiff's can be instantiated for a particular host, with different
name variables
in order to do that, the class also has to have the $installkeys variable that
can be passed to backupninja::client::key so that the second rdiff instantiation would
set installkeys => false, otherwise there will be an attempt to duplicate the resource