DL-197: Add DISCLAIMER file to the project
DL-197: Add DISCLAIMER file to the project

DISCLAIMER is missing for source release.

Author: Sijie Guo <sijie@apache.org>

Reviewers: Jia Zhai <zhaijia03@gmail.com>

Closes #125 from sijie/sijie/include_DISCLAIMER_file

sijie/incubator-distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog