[REEF-82]: Update pom.xml to publish Maven artifacts at Apache

This addressed the issue by using the Apache Parent POM.

JIRA: [REEF-82] (https://issues.apache.org/jira/browse/REEF-82)

Pull Request: Closes #42

Author:    Byung-Gon Chun <bgchun@apache.org>

cherry-picking commit 9739e49.