Ignore .Trashes directory

Currently node-dir will attempt to find all files and directories in a given path.  On a mac a `.Trashes` directory may exist which causes node-dir to exit with the following error:

```
/Users/daniel/Projects/bin/slurp.js:59
                if (err) throw err;
                               ^
Error: EACCES, readdir '/Volumes/Media/.Trashes'
```

When inspecting the `.Trashes` dir in bash it is clear this is a permissions issue.

```
$ ls -al
d-wx-wx-wt   2 daniel  staff    68 Jun  8 15:53 .Trashes
```

When inspecting `.Trashes` with fs.stat the `stat.mode` value is `17115`.  This can be reproduced by using chmod on any folder:

```
chmod 41333 ./TestFolder
```

This PR simply ignores directories with a mode of `17115`.  If merged this will resolve issue #11.