Readdir returns sub-subfolders

[dkumor]

Suppose the following folder structure:

test.txt
folder1/
   test2.txt

By default, http.File.Readdir in golang returns direct child files, so gives [test.txt, folder1/]

However, when I pack the files, File.Readdir seems to perform a recursive directory listing, and returns [test.txt,folder1,test2.txt] Note that test2.txt behaves as if it were in the root folder.

This causes issues in code using Readdir to recursively copy a directory from an embedded filesystem, and causes http.FileServer to give an incorrect listing when served without index.html

This issue is caused by https://github.com/rakyll/statik/blob/master/fs/fs.go#L163 , which does not check whether the file is in a subpath.

On a related note, empty directories are not listed at all, meaning that it would seem like they are non-existent.

[dkumor]

Just noticed there is already a PR for this at #55

[dkumor]

Fixed in #61