bugfix: Added puppetlabs/apt depedency and missing class include

Modulefile have a missing dependency for puppetlabs/apt, used when manage_repo = true

Also by puppetlabs/apt documentation you have to include the apt class first, before using any class defines (https://github.com/puppetlabs/puppetlabs-apt).

Without the include I get the following error:

 Could not find dependency File[sources.list.d] for Exec[add-apt-repository-ppa:chris-lea/redis-server] at /etc/puppet/modules/apt/manifests/ppa.pp:59