.travis.yml in suika-0.1.4 vs .travis.yml in suika-0.2.0

@@ -1,6 +1,12 @@
 ---
+os: linux
+dist: xenial
 language: ruby
 cache: bundler
 rvm:
-  - 2.7.0
-before_install: gem install bundler -v 2.1.2
+  - '2.5'
+  - '2.6'
+  - '2.7'
+
+before_install:
+  - gem install bundler -v 2.1.4