.travis.yml in slack-ruby-client-0.17.0 vs .travis.yml in slack-ruby-client-1.0.0

@@ -4,9 +4,10 @@
 
 rvm:
   - 2.5.3
   - 2.6.0
   - 2.7.1
+  - 3.0.2
   - ruby-head
   - jruby-head
 
 matrix:
   include: