Updated `.npmignore`
Updated `.npmignore`

- added `Gruntfile.js` - this file is only for development
- added `ghost-*.tgz` - this avoid packaging other packaged Ghost
  archives
- added `!core/frontend/src/admin-auth/*.html` - this re-adds the Admin Auth
  HTML file that would otherwise be excluded from the build

TryGhost/Ghost,TryGhost/Ghost,TryGhost/Ghost