Add mod_dir to the needed apache2 modules (kibana::apache)

Although the module might be loaded by the [default attributes of the apache2 cookbook](https://github.com/opscode-cookbooks/apache2/blob/master/attributes/default.rb#L161), someone might very well have overridden these.  So... explicitly including all dependencies FTW :)

Without mod_dir, accessing http://$IP:8400 will not get you to the dashboard `index.html`.
Merge pull request #17 from srenatus/patch-1

Add mod_dir to the needed apache2 modules (kibana::apache)

Looks like a sensible change,   tests out okay.   Merging.