Travis configuration - add animal-sniffer:check goal

Travis does not support Java versions prior to 1.8. There must be a way to check if Java 1.7+ compatible code wasn't accidentally introduced.

Author: gslowikowski

.travis.yml

@@ -8,6 +8,6 @@ install:
   - java -XX:+PrintFlagsFinal -version
   - mvn --version
 
-script: mvn verify --update-snapshots --settings .travis.settings.xml -e
+script: mvn verify animal-sniffer:check --update-snapshots --settings .travis.settings.xml -e
 
 jdk: oraclejdk8