Resolved duplicate package declaration error

Also simplified os lookup for packages.

Comment for mailplugins regarding undef

Fixed messed-up pathing for files and destinations.

Template wasn't generating correctly.

changed <% @whatever -%> to <%= @whatever %>.
Merge pull request #23 from tthayer/master

Fixed RHEL issues with init.pp and made auth-passwd template work.
update spec helper
adapted travis ci build
fixed sieve setup
updated lenses, using Jessie-shipped versions
install lences only on wheezy (squeeze being deprecated for ages now)
Huge corrections regarding dependencies between resources

After several tests, it seems there are many problems with dependencies,
especially when we're wanting to get the whole stuff set in one row.

The "exec dovecot" resource wasn't of any use, really. In additions,
some files were to be created *before* the package is installed, and
this made puppet crash with "no such file or directory" error.

The modifications allow to get a smooth, one-shot installation, with the
whole dependencies in the right order:
- packages
- then configurations
- then service
authorize lenses to be installed on other systems than Wheezy
added some more stuff to ignore