Expect composer-autoloader to be 1 dir up - in case it's not a symlink

I'm experiencing that the `bin/phpunit` binary installed by composer is not a symlink but a regular file.
The reason is that [vagrant copies symlinks as regular files](https://github.com/mitchellh/vagrant/commit/2a973df4401e1dc2d07c778080306582e48baab1) since recently, when the `rsync` shared-folder mechanism is used.

Wdyt about expecting this case in the binary?