Use both JDK7 and JDK8 in Travis
Fix javadoc compilation errors on jdk8
Merge pull request #1168 from nbelikov/1163_javadoc_for_jdk8

Fix JavaDoc compilation errors on JDK8
Merge pull request #1164 from WonderCsabo/travisJdk8

Use both JDK7 and JDK8 in Travis