End date shouldn't be included in month calculations

[mmallozzi]

When the end date is on the first of a month (e.g. October 1st), a request is issued both for dates in September and October. However, the end date is documented to be exclusive for this script, as it's the checkout date. So an extra unneeded request is being issued, which given the sensitive rate limiting on recreation.gov, would add to the instability.

Cause:
An rrule monthly rule includes the end date by default, so get_park_information ends up fetching for both months.

Solution:
I believe this can be solved by excluding the end date using exdate. Something like this:

start_of_month = datetime(start_date.year, start_date.month, 1)
ruleset = rrule.rruleset()
ruleset.rrule(rrule.rrule(rrule.MONTHLY, dtstart=start_of_month, until=end_date))
# exclude end date as that is the checkout date
ruleset.exdate(end_date)
months = list(ruleset)

I haven't robustly tested this to ensure it doesn't break other scenarios, but seems to work for my use case.