Sub-optimal result in relativeTo with fragment

URI("http://www.example.com:8080/dir/file#abcd").relativeTo('http://www.example.com:8080/dir/file').toString()

returns

./file#abcd ('#abcd' would have been better)

The more-optimal result seems to work with absoluteTo:

URI("#abcd").absoluteTo('http://www.example.com:8080/dir/file').toString()

returns

"http://www.example.com:8080/dir/file#abcd"

Great library, btw!
