[doc] amend changelog [ci skip]

Author: marscher

doc/source/CHANGELOG.rst

@@ -1,14 +1,16 @@
 Changelog
 =========
 
-2.5 (??-??-????)
+2.5 (02-09-2018)
 ----------------
 
 As of this version the usage of Python 2.7 is officially deprecated. Please upgrade
 your Python installation to at least version 3.5 to catch future updates.
 
 **New features**:
 
+- base: most Estimators and Models in msm, thermo and coordinates packages can be saved to disk now.
+  Multiple models/estimators can be stored in the same file, which uses HDF5 as backend. #849, 867, #1155, #1200, #1205
 - msm: Added Augmented Markov Models. A way to include averaged experimental
   data into estimation of Markov models from molecular simulations. The method is described in [1]. #1111
 - msm: Added mincount_connectivity argument to MSM estimators. This option enables to omit counts below