message: Update CHANGELOG to reflect new L2ElementRestriction class
diff: @@ -27,6 +27,10 @@ Miscellaneous
  the application level. Example usage of this new interface can be found
  in the examples/sundials directory.
  +- Added support for creating refined versions of periodic meshes, making use of
  + the new L2ElementRestriction class. This class also allows for computing
  + geometric factors on periodic meshes using partial assembly.
  +
  Version 4.0, released on May 24, 2019
  =====================================
  