Update Travis base OS to Xenial

gkrizek · gkrizek · commit a3b8b4366353 · 2018-12-28T08:26:31.000-06:00
Updating the base OS used in Travis to Xenial from Trusty. This also updates Docker to 18.06 instead of 17.06 in CI.
diff --git a/.travis.yml b/.travis.yml
@@ -1,4 +1,4 @@
-dist: trusty
+dist: xenial
 os: linux
 language: minimal
 cache:
