fix getFilenameMetaData with path module.

## Sample data with expanddir

before merge this request

```
// directory
{ extension: './documents/foo/bar',
  name: 'bar',
  location: './documents/foo',
  path: './documents/foo/bar',
  stat: 
   { dev: 0,
     mode: 16822,
     nlink: 1,
     uid: 0,
     gid: 0,
     rdev: 0,
     ino: 0,
     size: 0,
     atime: Wed Mar 05 2014 15:24:32 GMT+0900,
     mtime: Wed Mar 05 2014 15:24:32 GMT+0900,
     ctime: Mon Mar 03 2014 18:11:33 GMT+0900 } }
// file
{ extension: '.md',
  name: '/readme',
  location: './documents/foo/bar',
  path: './documents/foo/bar/readme.md' }
```

after merge this request

```
// directory
{ extension: '',
  name: 'bar',
  location: './documents/foo',
  path: './documents/foo/bar',
  stat: 
   { dev: 0,
     mode: 16822,
     nlink: 1,
     uid: 0,
     gid: 0,
     rdev: 0,
     ino: 0,
     size: 0,
     atime: Wed Mar 05 2014 15:24:32 GMT+0900,
     mtime: Wed Mar 05 2014 15:24:32 GMT+0900,
     ctime: Mon Mar 03 2014 18:11:33 GMT+0900 } }
// file
{ extension: '.md',
  name: 'readme',
  location: './documents/foo/bar',
  path: './documents/foo/bar/readme.md',
  stat: 
   { dev: 0,
     mode: 33206,
     nlink: 1,
     uid: 0,
     gid: 0,
     rdev: 0,
     ino: 0,
     size: 1773,
     atime: Wed Mar 05 2014 14:20:35 GMT+0900,
     mtime: Wed Mar 05 2014 14:20:35 GMT+0900,
     ctime: Wed Mar 05 2014 14:19:51 GMT+0900} }
```