added changelog

Author: pancetta

CHANGELOG.rst

@@ -1,6 +1,12 @@
 Changelog
 ---------
 
+- August 30, 2019: Version 3.1 adds many more examples like the nonlinear Schrödinger equation, more on Gray-Scott and in particular Allen-Cahn.
+  Those are many implemented using the parallel FFT library `mpi4pi-fft <https://bitbucket.org/mpi4py/mpi4py-fft/src/master/>`_, which can now be used with pySDC.
+  There are now 8 tutorials, where step 7 shows the usage of three external libraries with pySDC: mpi4py, FEniCS and petsc4py.
+  The MPI controller has been improved after performaning a detailed performance analysis using `Score-P <https://www.vi-hps.org/projects/score-p/>`_ and `Extrae <https://www.vi-hps.org/Tools/Extrae.html>`_.
+  Finally: first steps towards error/iteration estimators are taken, too.
+
 - February 14, 2019: Released version 3 of `pySDC`. This release is accompanied by the **ACM TOMS paper**
   `"pySDC --  Prototyping spectral deferred corrections" <https://doi.org/10.1145/3310410>`_.
   It release contains some breaking changes to the API. In detail: