add new `tempdir` function to Path::Class

[cho45]

Add new tempdir function to Path::Class which returns new Path::Class::Dir instance pointed to temporary directory.

This is just utility feature.

[kenahoo]

Thanks, that looks like a good idea. Could you also add docs for the new method?

[cho45]

I wrote doc. How about this?

[kenahoo]

Thanks, applied.

[cho45]

Thank you very much.