Expand rails 6.1 matrix

.travis.yml

@@ -38,9 +38,22 @@ script: "script/run_build 2>&1"
 
 matrix:
   include:
-    # Rails 6.1 builds (> 2.5)
+    # Rails 6.1 builds >= 2.5
+    - rvm: ruby-3.0.0-preview1
+      env: RAILS_VERSION='master'
+      allow_failure: true
     - rvm: 2.7.1
       env: RAILS_VERSION='master'
+    - rvm: 2.6.6
+      env: RAILS_VERSION='master'
+    - rvm: 2.5.8
+      env: RAILS_VERSION='master'
+      jdk: oraclejdk11
+      env:
+        - RAILS_VERSION='master'
+        - JRUBY_OPT=--dev
+        - JAVA_OPTS="--add-opens java.base/sun.nio.ch=org.jruby.dist --add-opens java.base/java.io=org.jruby.dist --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.security=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.base/java.security.cert=ALL-UNNAMED --add-opens=java.base/java.util.zip=ALL-UNNAMED --add-opens=java.base/java.lang.reflect=ALL-UNNAMED --add-opens=java.base/java.util.regex=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.io=ALL-UNNAMED  --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/javax.crypto=ALL-UNNAMED --add-opens=java.management/sun.management=ALL-UNNAMED"
+
     # Rails 6.0 builds >= 2.5.0
     - rvm: jruby-head
       jdk: oraclejdk11