Enable coverall report

Author: Sijie Guo <sijie@apache.org>
Author: Sijie Guo <sijieg@twitter.com>

Reviewers: Leigh Stewart <lstewart@apache.org>

Closes #33 from sijie/sijie/fix_coverall_plugin

.travis.yml

@@ -23,12 +23,10 @@ matrix:
 before_install:
   - echo "MAVEN_OPTS='-Xmx3072m -XX:MaxPermSize=512m'" > ~/.mavenrc
 
-install:
-  - travis_retry mvn -B install clean findbugs:check -U -DskipTests=true
-
 script:
   - travis_retry mvn clean apache-rat:check
-  - travis_wait 60 mvn package 
+  - travis_retry mvn clean install findbugs:check -DskipTests=true
+  - travis_wait 60 mvn package cobertura:cobertura coveralls:report
 
 cache:
   directories: