sphinxtogithub: keep the trailing / separator

def relative_path() relies on being able to replace values
including the / separator. Keep it there to retain the
original behavior.

Related-to: #1336
Ref: 1293e18
Signed-off-by: David Aguilar <davvid@gmail.com>

extras/sphinxtogithub/sphinxtogithub.py

@@ -97,7 +97,7 @@ class DirectoryHandler:
     def __init__(self, name, root, renamer):
         self.name = name
         self.new_name = name[1:]
-        self.root = str(root)
+        self.root = str(root) + os.sep
         self.renamer = renamer
 
     def path(self):