fileCallback add a additional param named filename

[zhangsanshi]

Sometimes I need to know the fullpath of a file,but I just can get the shortName.

[AckerApple]

My pull request addresses this by adding require('node-dir').files(path, 'all', callback, {shortName:true})

Check it out, working with package owner to make official: #40

fork location: https://github.com/AckerApple/node-dir

[AckerApple]

New pull request now includes options.shortName='relative' which allows all items to be returned but only with a value that is relative to the base path

#43