Deleting namespace using the generic interface fails

[pablochacin]

When trying to delete a namespace using the generic interface introduced in #70 the operation fails with the message object is being deleted: namespaces "namepspace-name" already exists.

This issue is probably related to an issue found in the create function that lead to introducing a logic for handling namespaces as a special case. The underlying problem is that namespaces cannot be accessed using a namespaced resource interface in the dynamic Kubernetes client.