ctags configuration

ctags let you generates a list of class/site/node/define which can then
be used by your texteditor to show up the puppet manifest
representation.

The configuration for ctags is done in /.ctags and ctags execution is
wrapped in a rake task 'tags' as a convenience.

Vim supports tags files and you can display the file structure using the
tagbar plugin.  The ctags configuration comes from:

  https://github.com/majutsushi/tagbar/wiki#puppet

I have added a `--languages=puppet` to restrict it to puppet manifests,
we might want to generate tags for python/php whatever script we have in
operations/puppet.

Change-Id: Ia164addddc48f897c3af092b1c14d80fb505889e