Updated test about small numbers

tests/test_rpnsymbol.py

 
     def test_value(self):
         sym = RpnSymbol(42, RpnSymbol.VALUE)
-        self.assertEqual(str(sym), '0x002A')
+        self.assertEqual(str(sym), '0x2A')
 
     def test_op(self):
         sym = RpnSymbol(0, RpnSymbol.OPERATION)