Verify that the site goal is working.

Currently you could not create the site with Java 8. Unfortunately I didn't know about this. In order to avoid such an accident we will build the site on the CI server, too.

Author: stefanbirkner

.travis.yml

@@ -1,5 +1,5 @@
 language: java
-script: mvn verify javadoc:javadoc
+script: mvn verify javadoc:javadoc site:site
 jdk:
   - oraclejdk7
   - oraclejdk8