Add support for setup.py clean -a
diff --git a/setup.py b/setup.py
index 7208e10..f4e9e18 100644
--- a/setup.py
+++ b/setup.py
@@ -8,7 +8,7 @@
 
 class CleanCommand(Command):
     user_options = [
-        ('all', None, '(Compatibility with original clean command)')
+        ('all', 'a', '(Compatibility with original clean command)'),
     ]
 
     def initialize_options(self):