Make commander a dev and build dependency and bump commander to latest version

[AlynxZhou]

Summary

Proposed change:

• Make commander a dev and build dependency:

It is only used in precompile script, people who install nunjucks as a dependency is unlikely to use precompile script.

• Bump commander to latest version.

Checklist

I've completed the checklist below to ensure I didn't forget anything. This makes reviewing this PR as easy as possible for the maintainers. And it gets this change released as soon as possible.

• [X] Proposed change helps towards purpose of this project.
• [X] Documentation is added / updated to describe proposed change.
• [X] Tests are added / updated to cover proposed change.
• [X] Changelog has an entry for proposed change (if user-facing fix or feature).

[AlynxZhou]

Should I update the docs to tell people who needs precompile to run npm install --include dev?