.travis.yml in i18n-js-3.0.3 vs .travis.yml in i18n-js-3.0.4

- old
+ new

@@ -7,15 +7,19 @@
 rvm:
   - 2.1.10
   - 2.2.8
   # Since the Travis Build Env does not recognize `2.3` alias yet
   # We need to specify the version precisely
-  - 2.3.5
-  - 2.4.2
+  - 2.3.6
+  - 2.4.3
+  - 2.5.0
   - ruby-head
 before_install:
 # Need to install something extra to test JS
 - npm install
+# Bundler 1.16.1 and rubygems 2.7.3 got issue
+# https://github.com/travis-ci/travis-ci/issues/8978#issuecomment-354036443
+- gem update --system
 gemfile:
   - gemfiles/i18n_0_6.gemfile
   - gemfiles/i18n_0_7.gemfile
   - gemfiles/i18n_0_8.gemfile
   - gemfiles/i18n_0_9.gemfile