Travis: use Trusty beta environment

Clement Champetier · Clement Champetier · commit 66b01748a1b7 · 2016-03-16T12:36:48.000+01:00
https://docs.travis-ci.com/user/trusty-ci-environment/
diff --git a/.travis.yml b/.travis.yml
@@ -1,7 +1,6 @@
 # Use container-based infrastructure
 sudo: false
-services:
-  - docker
+dist: trusty
 
 language: cpp
 
