Use working dir instead of file dir

`__DIR__` is the directory of the current file. If you run this file like that:
``` shell
composer require scrutinizer/ocular:~1.0.0
vendor/bin/ocular code-coverage:upload .....
```

It would not find the `autoload.php` file of Composer. This is because Composer symlinks `bin/ocular` to `vendor/bin/ocular`. This messes up with the path to `autoload.php`.