chore: prepare release notes

Midnighter · Midnighter · commit d05377175c67 · 2019-07-16T22:29:11.000+02:00
diff --git a/release-notes/0.15.4.md b/release-notes/0.15.4.md
@@ -0,0 +1,10 @@
+# Release notes for cobrapy 0.15.4
+
+## Fixes
+
+* This release brings a number of bug fixes for SBML I/O (#852).
+
+## Backwards incompatible changes
+
+* The deprecated `objective_coefficient` was removed (#871).
+
