Added root filesystem test (failing).

I propose being able to store files directly into the vfs without first having to create an arbitrarily named directory to store everything in since I believe that is counter-intuitive for new users. I propose doing this by calling `vfsStream::setup('/');`, or better still, make it the default behaviour when calling `vfsStream::setup();`.

The test I have attached currently fails with the following error:

>file_put_contents(vfs://foo): failed to open stream: "org\bovigo\vfs\vfsStreamWrapper::stream_open" call failed

Please make it work :)