Update to 1.3.1

CHANGELOG.md

 # Changelog of pygeodyn
 
+1.3.1 - 2020-02-03
+------------------
+Refactoring towards cleaner handling of PCA in augkf and zonkf:
+- PCA algorithms are now in dedicated objects
+- The Algo object is created through a factory function and will create the appropriate objects (Forecaster, Analysers)
+- Updated documentation in consequence
+
 1.3.0 - 2020-01-28
 ------------------
 Code structure improvements:

pygeodyn/_version.py

-__version__ = '1.3.0'
+__version__ = '1.3.1'
\ No newline at end of file

pygeodyn/release/RELEASE.md

-Copy this file and rename it as RELEASE.md and complete the parts in italics.
-
-RELEASE_TYPE: patch
-
-Refactoring towards cleaner handling of PCA in augkf and zonkf:
-- PCA algorithms are now in dedicated objects
-- The Algo object is created through a factory function and will create the appropriate objects (Forecaster, Analysers)
-- Updated documentation in consequence
\ No newline at end of file