Stringify destination for move_to method

Also whitespace cleanup.
Stringify destination for copy_to method
Updated POD for copy_to and move_to methods
Merge pull request #25 from robrwo/cp-mv-pod-fixes

Fixes for copy_to and move_to methods
Don't convert file into directory in subsumes()

Logically, even though both can't exist at the same time, the
directory /foo does not subsume the file /foo.
Merge pull request #26 from ilmari/fix-subsumes-file

Don't convert file into directory in subsumes()