message: Update changelog for 0.9.3
diff: Changelog
  =========
  +- 0.9.3
  + - mitigate bugs in ``middle_outer_views``, that will require breaking changes
  + in 0.10 to be fully fixed.
  + - Add scalar mul for {u,i}{8,16}
  + - Add CsMatBase::diag
  - 0.9.2
  - Fix a crash on matrix products with 0 rows.
  - 0.9.1
  