Support jdk 14 for travis CI

.travis.yml

@@ -4,7 +4,7 @@ branches:
   - stable
 language: java
 jdk:
-- oraclejdk8
+- openjdk14
 before_install:
 install:
 - mvn clean install -Dgpg.skip=true

pom.xml

@@ -493,6 +493,9 @@
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-javadoc-plugin</artifactId>
                 <version>3.2.0</version>
+                <configuration>
+                    <source>8</source>
+                </configuration>
                 <executions>
                     <execution>
                         <id>attach-javadocs</id>
@@ -506,7 +509,7 @@
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-gpg-plugin</artifactId>
-                <version>1.6</version>
+                <version>3.0.1</version>
                 <executions>
                     <execution>
                         <id>sign-artifacts</id>