define postgres version

Gummibeer · Gummibeer · commit 7a998367d6a8 · 2019-11-05T14:34:33.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -6,6 +6,9 @@ services:
   - mysql
   - postgresql
 
+addons:
+  postgresql: "9.4"
+
 cache:
   directories:
     - $HOME/.composer/cache/files
