.travis.yml in openpay-2.0.0 vs .travis.yml in openpay-2.0.1

@@ -1,3 +1,6 @@
 language: ruby
 rvm:
   - 2.4.2
+before_install:
+  - gem uninstall -v '>= 2' -i $(rvm gemdir)@global -ax bundler || true
+  - gem install bundler -v '< 2'