Add fileinfo to skip function

[tongjingran]

FileInfo is needed to determine whether the file needs to be skipped in many cases.

[tongjingran]

The Skip function looks like a callback function to judge the file should skip or not.
In golang project, package path/filepath has a similar type WalkFunc.
type WalkFunc func(path string, info os.FileInfo, err error) error
In most situaitions, simply providing the file name is not enough. Use an extra os.Stat operation is a waste of performance.

[otiai10]

You are right. It's gonna be v2 then with more refactoring because it's change of interface of this package