parse_duration() incorrectly parses nanoseconds

[siracusa]

Failing test below.

#!/usr/local/bin/perl

use strict;
use Test::More;
use DateTime::Format::Pg;

my $duration = DateTime::Format::Pg->parse_duration('7 years 00:00:00.000003');

is($duration->nanoseconds, 3000, 'nanoseconds duration.');

done_testing();

The output is:

not ok 1 - nanoseconds duration.
#   Failed test 'nanoseconds duration.'
#   at datetime_format_pg.pl line 11.
#          got: '3'
#     expected: '3000'
1..1

[lestrrat]

fixed in #17