Support for fseek().
$offset: The byte offset to got to.
$whence: SEEK_SET, SEEK_CUR, or SEEK_END.
TRUE on success.
Overrides StreamWrapperInterface::stream_seek
http://php.net/manual/streamwrapper.stream-seek.php
public function stream_seek($offset, $whence) {
// fseek returns 0 on success and -1 on a failure.
// stream_seek 1 on success and 0 on a failure.
return !fseek($this->handle, $offset, $whence);
}