Fix travis build

Author: henryju

.travis.yml

@@ -17,10 +17,3 @@ notifications:
   webhooks:
     - secure: "rgVuvy+z1Ehv03JZGDx5a8JPNPB8McXRropGKUo6TKvlzidjYD7nVOVF0NNSuzfCV1ZjbhDxY7MTzXtWetJlIYCtJNOP2VtM1oPeJIT98TybIbzcgdlMjWd3RBxo5K4fK4qhgDPSX53WPSzot/TqO3gkqyrjKpvRADJDVCMeWEY="
   on_start: always
-
-addons:
-  apt:
-    packages:
-      # upgrade java 8 as the default version 1.8.0_31 prevents from compiling sources
-      # https://github.com/travis-ci/travis-ci/issues/4042
-      - oracle-java8-installer