update cpanfile
update Changes for digest chunk_size option
fix 'remove' throwing

|| was checking whether the filename was itself true, rather than whether
unlink succeeded.

Also fixes documetation: by default C<unlink> never throws, so avoid
implying that it would throw when trying to delete a non-existent file.
deprecate dirname due to inconsistencies

Because 'dirname' as used by Path::Tiny might or might not give trailing
slashes, users don't know what to expect.  Rather than changing it to
always be one thing or the other, which might break people's code that
works around it, this commit just documents the problem and notes that
the method is deprecated.

Resolves #106.