Compile with oraclejdk8 not oraclejdk7

.travis.yml

@@ -1,6 +1,6 @@
 # Source language and JDK version to use
 language: java
-jdk: oraclejdk7
+jdk: oraclejdk8
 
 # Compile and package JAR and set build properties
 install: mvn package -DbuildNumber=$TRAVIS_BUILD_NUMBER -DciSystem=travis -Dcommit=${TRAVIS_COMMIT:0:7}