Fixed scanning to skip directories with no permissions instead of failing.

When 'scan' finds a directory to which it has not permissions, to fails instead of skipping it.

Reproduce original bug with:

```
mkdir 1
touch 1/file.txt
chmod 600 1
npm i rekuire

node
var rek = require('rekuire')
```

This could be more cleanly solved by using fs.stat instead of fs.statSync, but that would rekuire some work... :]