remove config.js on uninstall

modified:   index.js
- remove unused afterInstall function
- created uninstall function
  - remove config folder

modified:   package.json
- version bump
removed string-format; version bump
added rimraf
fixed typo; chownSync -> chmodSync
Merge pull request #369 from tjwebb/uninstall-remove-configjs

remove config.js on uninstall