Replace left(), right(), and __reversed__() with the more general purpose

__getitem__() and __setitem__().

Simplifies the API, reduces the code size, adds flexibility, and makes
deques work with bisect.bisect(), random.shuffle(), and random.sample().

Lib/asynchat.py

@@ -262,7 +262,7 @@ class fifo:
         return self.list == []
 
     def first (self):
-        return self.list.left()
+        return self.list[0]
 
     def push (self, data):
         self.list.append(data)