This allows an override of the default DirectoryIndex directive in dir.conf.erb
Updated in response to comments from @hunner; fix typo, handle Arrays in the template, and move logic from template to class.
Add basic spec test for mod_dir

Note: No package test as it seems mod_dir is distributed _with_ the Apache package.
Removing repeated text from bad cut/paste
Restructuring prior to sorting out parametric tests
Changing precondition so apache does not declare apache::mod::dir, which should allow parametric tests.

Thanks to @hunner
And repeat tests for RedHat OS family
Merge pull request #211 from nesi/directoryindex

This allows an override of the default DirectoryIndex directive