[REEF-16]: Update the NOTICE, LICENSE, ... to ASF standards

This addressed the issue by adding ASF-compliant NOTICE and LICENSE
files, removing old LICENSES.txt and NOTICES.txt, and updating README.md
to meet ASF standards.

JIRA: [REEF-16](https://issues.apache.org/jira/browse/REEF-16)

Pull Request: Closes #40

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