WIP: Add spec tests and fix bug with package installer on Ubuntu.

There appears to be a bug with how `value_for_platform_family` is used in the `vim::package` recipe. I've fixed this issue and added a chefspec regression test. 

However there's an issue with `value_for_platform_family` when using a `platform` *other* than `ubuntu` or `debian`. The odd thing is that choosing `value_for_platform_family` works for APT-based distros, but uses the `default` value for RPM-based ones. I haven't tested on other platforms.

This has two failing tests as a result.