Ran 2to3 on pillar + some manual fixups

The 'manual fixups' are:

- incorrect use of dict.items() where dict.iteritems() was meant; this
  results in list(dict.items()), which I changed to dict.items().
- removal of 'from __future__ import' lines, which 2to3 changes into
  empty lines; I removed the empty lines.

pillar/api/file_storage/moving.py

@@ -29,7 +29,7 @@ def change_file_storage_backend(file_id, dest_backend):
     Files on the original backend are not deleted automatically.
     """
 
-    dest_backend = unicode(dest_backend)
+    dest_backend = str(dest_backend)
     file_id = ObjectId(file_id)
 
     # Fetch file document