nth day-of-the-week

[Rob]

This is an awesome project. Thank you for making it open source.

Quick question: I see that later.js supports this syntax:
later.parse.text('on the 1st day of the month at 1:00 pm every 3 months');

but I doesn't seem to work with:
later.parse.text('on 1st Monday of the month at 13:00 every 3 months')
...
later.parse.text('on last Monday of the month at 13:00 every 3 months')

[Rob]

Found this: #151
Thank you!