Fix #80.

@erasche mentioned in the following comment (#80 (comment)) this is actually a useful feature sometimes - so in 2e41e0a I implemented an option to save all of Galaxy's state not just the files directory which should be even more useful.

planemo/galaxy_config.py

@@ -140,7 +140,7 @@ def config_join(*args):
             log_level=kwds.get("log_level", "DEBUG"),
         )
         properties = dict(
-            file_path="${temp_directory}files",
+            file_path="${temp_directory}/files",
             new_file_path="${temp_directory}/tmp",
             tool_config_file=tool_conf,
             check_migrate_tools="False",