Revert ExtensionClass 2.13 change for now, it breaks CMF tests and we should...

Revert ExtensionClass 2.13 change for now, it breaks CMF tests and we should try to understand what exactly happens here

doc/CHANGES.rst

@@ -98,7 +98,6 @@ Features Added
 
 - Updated packages:
 
-  - ExtensionClass = 2.13.0
   - zope.annotation = 3.5.0
   - zope.app.form = 3.12.1
   - zope.broken = 3.6.0

versions.cfg

@@ -7,7 +7,7 @@ ClientForm = 0.2.10
 DateTime = 2.12.0
 distribute = 0.6.10
 docutils = 0.6
-ExtensionClass = 2.13.0
+ExtensionClass = 2.12.0
 Jinja2 = 2.2.1
 mechanize = 0.1.11
 Persistence = 2.12.0