Document deprecation of this package.

README.rst

@@ -5,3 +5,7 @@ A storage implementation which uses RAM to persist objects, much like
 MappingStorage. Unlike MappingStorage, it needs not be packed to get rid of
 non-cyclic garbage and it does rudimentary conflict resolution. This is a
 ripoff of Jim's Packless bsddb3 storage.
+
+**Please note: Usage of this package is deprecated, as it is known to randomly loose data, especially with zope 4.**
+
+For details see: https://github.com/zopefoundation/tempstorage/issues/8