explicitly call jacoco:merge

.travis.yml

@@ -78,5 +78,5 @@ matrix:
     env: HEADLESS=true STATIC=false
 
 after_success:
-  - if [[ "$TRAVIS_OS_NAME" == "linux" && "$HEADLESS" == "false" ]] ; then mvn jacoco:report coveralls:report -U -P travis-coverage ; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" && "$HEADLESS" == "false" ]] ; then mvn jacoco:merge jacoco:report coveralls:report -U -P travis-coverage ; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" && "$HEADLESS" == "false" ]] ; then JACOCO_SOURCE_PATH=java/src ./cc-test-reporter format-coverage target/site/jacoco/jacoco.xml --input-type jacoco ; ./cc-test-reporter upload-coverage ; fi