Merge pull request #39 from sathieu/for_upstream

Ensure apt.conf and apt_preferences files are removed when requested
Fix exec in source, updated some tests
Fix exec subscription
Fix apt.conf handling
Fix specs
Move dependency to puppetlabs' concat
Merge pull request #40 from netmanagers/master

Fix some bugs in sources.pp and init.pp, fix specs.
unattended-upgrades: Base config on current from jessie (0.82.7)

This also replaces the old syntax "OO AA" with o=OO, a=AA
unattended-upgrades: Use better Origins-Pattern
unattended-upgrades: Enable -updates (ex "volatile")
unattended-upgrades (<< 0.70) doesn't support Origins-Pattern