Add 3.1-stable to tested branches list
diff --git a/.travis.yml b/.travis.yml
index b32390d..5815c95 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -46,4 +46,5 @@
   only:
     - develop
     - 3.0-stable
+    - 3.1-stable
     - /^feature\/.+$/