WIP: Add update action
This will close #4.
In order to properly update, root access is required. In order to not fuck up all files, rule.GetOwner() should return the username of the user using sudo, and rule.GetGroup() should return the main group name of the user using sudo. Sadly, the functionality for group name management is not yet available in Go, but is planned for Go 1.6. This MR will therefore be stalled untill Go 1.6 releases.