.travis.yml in test-tracer-1.1.2 vs .travis.yml in test-tracer-1.1.3

@@ -1,5 +1,7 @@
 sudo: false
 language: ruby
 rvm:
-  - 2.3.4
+  - 2.2
+  - 2.3
+  - 2.4
 before_install: gem install bundler -v 1.15.3