Update changelog

CHANGELOG.rst

+Unreleased changes
+------------------
+
+Version 3
+---------
+3.1 / 2020-02-28
+~~~~~~~~~~~~~~~~
+* removed ROOT dependency. ``jppy`` now only depends on a few Jpp headers
+
+3.0 / 2020-02-27
+~~~~~~~~~~~~~~~~
+* **Major overhaul!** Dropped all the DAQ readout functionality in favour
+  of `km3io https://git.km3net.de/km3py/km3io`_
+* Introduced the ``jppy.pdf`` module which has a wrapper class ``JMuonPDF``
+  to access Jpp PDF methods
+
+Version 2
+---------
+2.1 / 2019-10-06
+~~~~~~~~~~~~~~~
+* Automatic discovery of libraries for ROOT 5 and 6
+
+2.0 / 2018-12-20
+~~~~~~~~~~~~~~~
+* Support for Jpp 9+
+
+Version 1
+---------
+
+1.6 / 2017-12-04
+~~~~~~~~~~~~~~~
+* depend on latest jpp trunk (method renaming grrrrr) (find in THRONG)
+* fix build script (was broken in 1.5.1, apparently)
+
+1.5.1 / 2017-11-21
+~~~~~~~~~~~~~~~~~
+* minor bugfixes. jfitreader now works (and has a km3pipe pump)
+* DON'T USE
+
+1.5.0 / 2017-11-21
+~~~~~~~~~~~~~~~~~
+* Add preliminary jfit reader
+
+1.4.0 / 2017-10-19
+~~~~~~~~~~~~~~~~~
+* Adds timeslice and summary pump (preliminary)