put temporary data file in the same director as the data file itself

This should make shutil.move use rename, which is atomic, avoiding
losing data when interweaving writes happen.

This will close wting#358.

bin/autojump_data.py

@@ -120,11 +120,12 @@ def migrate_osx_xdg_data(config):
 
 def save(config, data):
     """Save data and create backup, creating a new data file if necessary."""
-    create_dir(os.path.dirname(config['data_path']))
+    data_dir = os.path.dirname(config['data_path'])
+    create_dir(data_dir)
 
     # atomically save by writing to temporary file and moving to destination
     try:
-        temp = NamedTemporaryFile(delete=False)
+        temp = NamedTemporaryFile(delete=False, dir=data_dir)
         # Windows cannot reuse the same open file name
         temp.close()