Github user prabhjyotsingh commented on the issue:
https://github.com/apache/zeppelin/pull/2717
Selenium 3.x requires JDK8, guava-23, google.gson-2.8.2, which was
conflicting with existing zeppelin-server package, hence have moved if to
selenium testing to a new package called "zeppelin-integration".
Also in the Travis matrix have change dist to trusty (which might be
required for ZEPPELIN-3118) and set JDK as oraclejdk8.
cc: @felixcheung , @jongyoul , @Leemoonsoo , @zjffdu ---
