Drop Oracle JDK 8, add OpenJDK 13.
diff --git a/.travis.yml b/.travis.yml
index a069d27..6789d48 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,30 +1,30 @@
-# Licensed to the Apache Software Foundation (ASF) under one or more
-# contributor license agreements.  See the NOTICE file distributed with
-# this work for additional information regarding copyright ownership.
-# The ASF licenses this file to You under the Apache License, Version 2.0
-# (the "License"); you may not use this file except in compliance with
-# the License.  You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-language: java
-sudo: false
-
-jdk:
-  - openjdk7
-  - openjdk8
-  - openjdk11
-  - openjdk12
-  - oraclejdk8
-
-script:
-  - mvn
-
-after_success:
-  - mvn clean test jacoco:report coveralls:report -Ptravis-jacoco
+# Licensed to the Apache Software Foundation (ASF) under one or more

+# contributor license agreements.  See the NOTICE file distributed with

+# this work for additional information regarding copyright ownership.

+# The ASF licenses this file to You under the Apache License, Version 2.0

+# (the "License"); you may not use this file except in compliance with

+# the License.  You may obtain a copy of the License at

+#

+#     http://www.apache.org/licenses/LICENSE-2.0

+#

+# Unless required by applicable law or agreed to in writing, software

+# distributed under the License is distributed on an "AS IS" BASIS,

+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

+# See the License for the specific language governing permissions and

+# limitations under the License.

+

+language: java

+sudo: false

+

+jdk:

+  - openjdk11

+  - openjdk12

+  - openjdk13

+  - openjdk-ea

+  - oraclejdk8

+

+script:

+  - mvn

+

+after_success:

+  - mvn clean test jacoco:report coveralls:report -Ptravis-jacoco