SAMZA-1409; add missing parts and make guideline clearer for docs/README.md
SAMZA-1409; add missing parts and make guideline clearer for docs/README.md

Author: Fred Ji <haifeng.ji@gmail.com>

Reviewers: Jagadish <jagadish@apache.org>

Closes #288 from fredji97/master_docs_readme

abhishekshivanna/samza,lhaiesp/samza,prateekm/samza,bharathkk/samza,apache/samza,prateekm/samza,lhaiesp/samza,fredji97/samza,bharathkk/samza,lhaiesp/samza,prateekm/samza,bharathkk/samza,abhishekshivanna/samza,TiVo/samza,bharathkk/samza,lhaiesp/samza,TiVo/samza,prateekm/samza,bharathkk/samza,TiVo/samza,abhishekshivanna/samza,fredji97/samza,apache/samza,abhishekshivanna/samza,apache/samza,prateekm/samza,TiVo/samza,fredji97/samza,apache/samza,fredji97/samza,lhaiesp/samza,TiVo/samza,fredji97/samza,abhishekshivanna/samza,apache/samza