Fixes #24: Explain -d flag in cli help and documentation

[manrajgrover]

Description of new feature, or changes

This PR fixes #24 explaining -d flag for fixtures command in cli help and documentation.

Checklist

• [x] Your branch is up-to-date with the base branch
• [ ] You've included at least one test if this is a new feature
• [x] All tests are passing

Related Issues and Discussions

Fixes #24

People to notify

@sartaj10