Leading zeroes ignored in parsing of milliseconds

[dvorakroth]

The Problem

When parsing a time that includes an amount of milliseconds under 100, the parse function erroneously ignores the leading zeroes.

Steps to reproduce

const PostgresInterval = require('postgres-interval');

console.log(PostgresInterval('04:20:00.069').milliseconds); // should print 69, instead prints 690

[charmander]

i am not surprised this was hiding in #48

[bendrucker]

Haven't had a chance to fix this yet but happy to review a fix ASAP from anyone who wants to contribute one.