.travis.yml in twilio-ruby-5.0.0.rc21 vs .travis.yml in twilio-ruby-5.0.0.rc22

@@ -3,9 +3,11 @@
 cache: bundler
 bundler_args: --without development
 rvm:
   - ruby-head
   - ruby
+  - 2.4.0
+  - 2.3.0
   - 2.2.0
   - 2.1.0
   - 2.0.0
   - jruby-head
   - jruby