Update travis configuration.

.travis.yml

@@ -1,7 +1,6 @@
 language: ruby
 cache: bundler
 dist: xenial
-env: OS="xenial 16.04"
 bundler_args: --without development
 
 after_script:
@@ -10,22 +9,29 @@ after_script:
 matrix:
   fast_finish: true
   include:
+    - rvm: 2.4
+    - rvm: 2.4
+      os: osx
+      osx_image: xcode10.2
+    - rvm: 2.5
     - rvm: 2.6
       env: NIO4R_PURE=true
-    - rvm: 2.3
-      dist: trusty
-      env: OS="trusty 14.04"
-    - rvm: 2.4.6
+    - rvm: 2.6
+    - rvm: 2.6
+      dist: bionic
+    - rvm: 2.6
       os: osx
-      osx_image: xcode10.2
-      env: OS="osx xcode 10.2"
+    - rvm: 2.7
     - rvm: truffleruby
     - rvm: truffleruby
       env: NIO4R_PURE=true
+    - rvm: jruby
+      env: JRUBY_OPTS="--debug -X+O --dev -J-Djruby.launch.inproc=true -J-Xmx1024M"
     - rvm: jruby-head
       env: JRUBY_OPTS="--debug -X+O --dev -J-Djruby.launch.inproc=true -J-Xmx1024M"
     - rvm: ruby-head
   allow_failures:
     - rvm: ruby-head
     - rvm: truffleruby
     - rvm: jruby-head
+    - rvm: jruby