chore: add release notes

Midnighter · Midnighter · commit d8949e927b72 · 2019-04-26T16:42:04.000+02:00
diff --git a/release-notes/0.15.3.md b/release-notes/0.15.3.md
@@ -0,0 +1,8 @@
+# Release notes for cobrapy 0.15.3
+
+## Fixes
+
+* Correct multiple issues with the new SBML parser (#822, #839, #840, #843,
+  #844).
+* Function `validate_sbml_model` properly captures errors and warnings.
+
