Update CHANGELOG

Author: ajjackson

CHANGELOG.rst

@@ -17,6 +17,11 @@
   - ``get_args()`` function removed from ``euphonic.cli.utils``; this
     was previously simplified to a one-liner so brings no DRY benefit.
 
+  - ``euphonic.cli.utils`` has been broken up into submodules. All the
+    appropriate functions are re-exported to ``__all__`` so this
+    should not break API in practice, but e.g. Quantity can no longer
+    be imported from ``euphonic.cli.utils``.
+
 - Features
 
   - Spectrum1DCollection and Spectrum2DCollection can be indexed with