travis: use more recent version of Ubuntu

noxdafox · noxdafox · commit 98c2c94b207e · 2018-12-09T22:42:31.000+02:00
Signed-off-by: Matteo Cafasso &lt;noxdafox@gmail.com&gt;
diff --git a/.travis.yml b/.travis.yml
@@ -1,3 +1,4 @@
+dist: xenial
 language: elixir
 elixir: '1.6.6'
 otp_release:
