Update to Java 11

Author: stefan-ka

.travis.yml

@@ -1,7 +1,7 @@
 language: java
 
 jdk:
-- openjdk8
+- openjdk11
 
 script:
   - |

build.gradle

@@ -47,6 +47,10 @@ dependencies {
     testRuntimeOnly "org.junit.jupiter:junit-jupiter-engine:${jUnitVersion}"
 }
 
+configurations {
+    testImplementation.exclude module: 'graphviz-java'
+}
+
 task sourcesJar(type: Jar) {
     from sourceSets.main.allJava
     archiveClassifier = 'sources'