Addresses issue #5.

Added license and tags reference to photos->by_id sub.

    $result = $api->photos->by_id([<photo_id>]);
    print "Licnese: " . $result->{license} . "\n";
    print "Raw tags:  ";
    for my $i (@{ $result->{tags} } ){
            print $i->{raw} . "\n";
    }