Added mechanism to check for the template file via a heirarchy of paths

Will now look in a couple of other places to see if there is a template file instead of just the default one built into drud gem.

Will  check for a template file at:

* `<current cookbook path>/templates/default/README.md.erb`
* `~/.chef/README.md.erb`
* `<Path to Drud Gem>/templates/readme.md.erb`

It checks in the order shown and the first one it finds, it will use.