[MARVIN-21] Travis CI sbt batch mode

Our Travis-CI failed while checking the latest master merge.
https://travis-ci.org/apache/incubator-marvin/jobs/470011726
By adding a `-batch` to sbt, the build should fail and start retrying right after sbt project loading fail.
diff --git a/.travis.yml b/.travis.yml
index 08689ac..3628d48 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -30,7 +30,7 @@
       before_script:
         - cd engine-executor
         - unset SBT_OPTS
-      script: travis_retry sbt ++$TRAVIS_SCALA_VERSION coverage test coverageReport
+      script: travis_retry sbt -batch ++$TRAVIS_SCALA_VERSION coverage test coverageReport
     # Python Toolbox
     # Python Toolbox - Linux
     - language: python