Drop Oracle JDK 8, add OpenJDK 13.
diff --git a/.travis.yml b/.travis.yml
index 4d25cf4..88f36fb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,10 +17,10 @@
 sudo: false

 

 jdk:

-  - oraclejdk8

   - oraclejdk11

   - openjdk8

   - openjdk11

   - openjdk12

+  - openjdk13

   - openjdk-ea