apt module must install debian/ubuntu-keyring package to prevent future problems with package signing
apt: improvements

* added modulefile/license files
* removed puppet-common dependencies
* use fqdn_rand() built-in instead of ip_to_cron()
* apt support preferences.d since version >= 0.7.22
apt: typo + rm old README
apt: README.md tuning
apt: README.md tuning
syntax checking with puppet-lint + cosmetics
apt::key: add new keyserver option
Merge pull request #30 from fredj/keyserver

apt::key: add new keyserver option
fixing potentially invalid monthday parameter

The "monthday" parameter of cron resources cannot be 0; however, the
code that generates a random value for that parameter in apt::clean can
sometimes generate a 0 value.  This patch changes the behavior slightly
in order to generate values between 1 and 28 inclusive.
apt::preferences - avoid whitespace in filenames.
Merge pull request #31 from hakamadare/monthday-fix

fixing potentially invalid monthday parameter
Move globals from clean to params making apt::clean parameterized
Lint apt::preferences
Lint apt::key
lint apt::params
Merge pull request #36 from mcanevet/lint

Lint
Support updating of expired keys
Support apt::preferences for apt < 0.7.22
Merge pull request #38 from raphink/preferences_lenny

Support apt::preferences for apt < 0.7.22
added unattended-upgrades config for wheezy