Write a quickstart document to v3

[tisonkun]

... or update the README.md file.

This continues the discussion on slack. Refs:

• https://lists.apache.org/thread/l6sqm8ygrw9hym9rn5ftrd87jpjtro05

Some encountered issues:

• Directory structure is significant
• [RESOLVED] How to generate fake data
• [RESOLVED] How to load ldap data and when to reload
• [RESOLVED] Env setup