.travis.yml in opentok-3.1.0 vs .travis.yml in opentok-4.0.0

@@ -3,13 +3,15 @@
 language: ruby
 # Travis bug, see https://github.com/bundler/bundler/pull/3559
 cache: bundler
 before_install: gem update bundler
 rvm:
-- 2.0
 - 2.1
 - 2.2
 - 2.3
 - 2.4
+- 2.5
+- 2.6
+- 2.7
 notifications:
   slack:
     secure: agVll2R9PTPvJMcUgbvOh9eGt60zGDc8kPUwEsiQr828rCgXh/ZxD5irYDyKQg3ZsS8+f3MjFCwzU7uQALkia2pDrie9d8g8m1dt4Q5U7Qm6QecshvE0U9JwbB5Ngxaftbqyf0XEFrE7CKs7RI1BzFRpe8m+fdZgfwccX8Gb7pc=