[DISCUSS] Improve the technical documentation

[Gang(Gary) Wang]

As Niall mentioned suggestion and issues on MNEMONIC-360
<https://issues.apache.org/jira/browse/MNEMONIC-360>, I think we need put
more efforts on technical documentation after the release of
0.9.0-incubating. so I create this DISCUSS thread for discussion about
where and how to improve it. please join us and help us to prioritize the
next work items. Thanks!