add changelog for v0.681

Author: joergbuchwald

CHANGELOG.md

@@ -2,8 +2,16 @@
 
 All notable changes to **VTUinterface** will be documented in this file.
 
+## [0.681]
+* new tool that enables spatial transformation of slices
+* more functionalities to read and interpolate cell data based on cell center points
 
-## [0.67]
+## [0.68]
+* changes in interface to distinguish between cell data an point data
+* filename argument of PVDIO contains now the directory argument as well (the folder keyword argument is dropped)
+* more tests
+* VTUinterface can deal with different orientations for 1d and 2d
+* VTK backend is added to enable better interpolation as voronoi based interpolation in scipy often fails
 
 ### Bugfixes