misc: remove manual changelog from README.txt

README.txt

@@ -37,32 +37,3 @@ fields, in order to allow to match them in payment system backoffice. They are:
 
 For other backends, the order and transaction ids, separated by '!' are sent in
 order id field, so they can be matched in backoffice.
-
-Changelog
-=========
-
-1.8
----
-- fix UTF-8 character in non unicode log message
-
-1.7
----
-- check responses and raise ResponseError when theyr are malformed
-
-1.6
----
-- fix payzen service_url
-- rationalize Payment object constructors
-
-1.5
----
-- uniformize constructors
-- fix service_url in the payzen backend
-
-1.4
----
-- add sips2 backend to conform with version 2.3 of their interface
-
-1.3
----
-- add payzen backend