.travis.yml in protocol-http2-0.9.1 vs .travis.yml in protocol-http2-0.9.2

@@ -2,9 +2,10 @@
 dist: xenial
 cache: bundler
 
 matrix:
   include:
+    - rvm: 2.3
     - rvm: 2.4
     - rvm: 2.5
     - rvm: 2.6
     - rvm: 2.6
       env: COVERAGE=PartialSummary,Coveralls