.travis.yml in gibbon-3.3.4 vs .travis.yml in gibbon-3.4.0

@@ -2,10 +2,11 @@
 sudo: false
 cache: bundler
 before_install:
   - gem install bundler # -v 1.7.14 if a specific version is needed
 rvm:
-  - 2.3.8
   - 2.4.5
   - 2.5.7
   - 2.6.5
   - 2.7
+  - 3.0.0
+