Update changelog

Author: njoyce

CHANGES.txt

@@ -8,6 +8,12 @@ versions of PyAMF.
 
 0.7 (Unreleased)
 ----------------
+- Dropped support for Python 2.5. A Python 3 port is underway.
+- Fix a rare string collision bug with AMF3 #36
+- Updated to use the latest version of Cython (0.21.2) #34
+- Added Travis/coveralls support.
+- Add post processing callbacks to finalise the decoded payloads. #45
+- Added support for `google.appengine.ext.ndb`. #47
 - ``pyamf.Undefined`` now evaluates to ``False`` in a boolean expression
   (:ticket:`827`)
 - Fixed an issue in the client where '; charset=utf8' would be appended to the