Add a warning if someone includes users::default

It does nothing and people should know that. Including it on the run list to get the LWRPs is the wrong way to load dependent libraries. Depend on it in your metadata.

Signed-off-by: Tim Smith <tsmith@chef.io>

recipes/default.rb

@@ -17,4 +17,4 @@
 # limitations under the License.
 #
 
-# Empty default recipe for including LWRPs.
+Chef::Log.warn('The default users recipe does nothing. See the readme for information on using the users resources')