.travis.yml in progress-3.5.1 vs .travis.yml in progress-3.5.2

@@ -1,5 +1,6 @@
 sudo: false
+dist: trusty
 language: ruby
 before_install:
   - gem install bundler || gem install bundler --version '< 2'
 rvm:
   - '1.9.3-p551'