Skipping doclint if building with Java 8. It breaks the build due to err...

...ors in eureka javadoc (this strict doclint checking affects whole world really).

I'm a casual gradle user so the solution might not be the best one for this particular project. I just copied (and tested) solution posted on Stephen Colebourne's blog: http://blog.joda.org/2014/02/turning-off-doclint-in-jdk-8-javadoc.html