Add ability to handle pathlib paths

- Handle pathlib paths across all implementations, plat_other already did
- Move preprocessing code to common location

send2trash/plat_gio.py

@@ -6,11 +6,11 @@
 
 from gi.repository import GObject, Gio
 from .exceptions import TrashPermissionError
+from .util import preprocess_paths
 
 
 def send2trash(paths):
-    if not isinstance(paths, list):
-        paths = [paths]
+    paths = preprocess_paths(paths)
     for path in paths:
         try:
             f = Gio.File.new_for_path(path)