Add default apt repositories

Using attribute-based apt repositories allows overriding of the attribute to allow the use of internal repository mirrors.
Use attribute-based instead of instead of hard-coded apt repositories

Using attribute-based apt repositories allows overriding of the attribute to allow the use of internal repository mirrors.
Update Canonical Cloud Archive Signing Key

The previous key did not return a result whenever 'apt-key list | grep #key' was run, causing the key to be downloaded on every run.
Fix foodcritic errors FC043, FC045
Merge pull request #83 from odyssey4me/folsom

Use attribute-based instead of instead of hard-coded apt repositories