recommend doing this such that 'true' is also acceptable.

spec tests that test `true` and `'true'`
See https://github.com/ghoneycutt/puppet-module-ssh/blob/master/spec/classes/init_spec.rb#L871

validation and type handling in manifest
https://github.com/ghoneycutt/puppet-module-facter/blob/master/manifests/init.pp#L28-33