Use Xenial on Travis instead of Trusty

TartanLlama · TartanLlama · commit 12df7d710cb9 · 2019-06-25T10:22:54.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,6 +1,6 @@
 language: cpp
 
-dist: trusty
+dist: xenial
 sudo: false
 
 matrix:
