Comment reasoning
Handle options at entry point
-- whitespace
Improve, expose and document cache functionality
-- grammar
Cleanup
Cleanup and documentation of resolveExternal
Remove obsolete function
Update documentation link
Refactored relative module resolution.

It's now 100% up to Node.js standard.
Remove commented out logs
Remove obsolete code
-- whitespace
Cache stat results during one pass
Demand file extensions (.js or .json)
Bulletproof dir constraint
-- whitespace
No recurrency for package.json:main resolution
Do not rely on case of extension
Improve client-side resolution logic