Cleanup ~/.cache/fus metadata before fus exits. #71

Hi,

I have found out fus is storing cached metadata in ~/.cache/fus. This is quite OK, but it should try to remove them once it finishes using it. I understand that in case of crash or some unpredictable issue, the metadata can stay there, but I think generally it should remove it.

So far I have to add following cronjob to clean that directory to composer machine we use:

find ~/.cache/fus -type f -mtime +1 -exec rm {} ;