[Issue 5] Publishing snapshot artifacts to JCenter

[yangb8]

This is a similar code change of https://github.com/pravega/flink-connectors/pull/129

Test

• docker run --name artifactory -d -p 8081:8081 docker.bintray.io/jfrog/artifactory-oss
• ./gradlew publishToRepo -PpublishUrl=http://localhost:8081/artifactory/example-repo-local/ -PpublishUsername=admin -PpublishPassword=password
• http://localhost:8081/artifactory/example-repo-local/io/pravega/hadoop-connectors/ hadoop-connectors-0.3.0-16.4331d47-20180523.183352-1-javadoc.jar 23-May-2018 18:33 31.84 KB hadoop-connectors-0.3.0-16.4331d47-20180523.183352-1-sources.jar 23-May-2018 18:33 6.76 KB hadoop-connectors-0.3.0-16.4331d47-20180523.183352-1.jar 23-May-2018 18:33 22.43 MB hadoop-connectors-0.3.0-16.4331d47-20180523.183352-1.pom 23-May-2018 18:33 1.55 KB maven-metadata.xml 23-May-2018 18:33 374 bytes

Also uploaded to jfrog

https://oss.jfrog.org/artifactory/jfrog-dependencies/io/pravega/pravega-connectors-hadoop/0.3.0-18.a042f0c-SNAPSHOT/ ../ maven-metadata.xml 24-May-2018 21:40 1.23 KB pravega-connectors-hadoop-0.3.0-18.a042f0c-20180524.214012-1-javadoc.jar 24-May-2018 21:40 33.24 KB pravega-connectors-hadoop-0.3.0-18.a042f0c-20180524.214012-1-sources.jar 24-May-2018 21:40 6.79 KB pravega-connectors-hadoop-0.3.0-18.a042f0c-20180524.214012-1.jar 24-May-2018 21:40 22.43 MB pravega-connectors-hadoop-0.3.0-18.a042f0c-20180524.214012-1.pom 24-May-2018 21:40 1.55 KB

[yangb8]

any other comments?