This change enables the user to diff between two environments that are
either local or remote.

i.e.,

`kubecfg diff local:dev local:prod` will diff between the expanded
templates for each environment on disk.

`kubecfg diff remote:dev remote:prod` will diff between two remote
environment clusters. It does this by first expanding the component
templates of each environment. Then, the live objects are fetched from
each of the clusters and the diff is performed against the live objects.

`kubecfg diff local:dev remote:prod` is also an option. This will diff
between the expanded templates for 'dev' on disk and the live objects
on 'prod's server.

- Move fqname to utils
- Add ResourceNameFor and use it to get a lowercased/pluralised
  version of the resource name

Fixes #15

Annoyingly, delete options `OrphanDependents` and `PropagationPolicy`
are mutually exclusive.  This change compares the k8s server version
to see if the server is going to look for the newer PropagationPolicy.

Fixes a78be141 (aka PR #59)