TTL should probably use the interval minutes or lower

[andela-oakinniranye]

@oscartbeaumont the package doesn't set a TTL explicitly, hence netlify defaults to 1hr. However, given a 5-min default update interval, I was thinking it'd probably be better for the TTL to reflect that interval or something lower to reduce the dns cache time.
For example, i think some dns updating services defaults to like 60 seconds

[oscartbeaumont]

I think this makes sense, I think the best way to add this would be to have the TLL default to the update interval but add another command line flag which would act as an override in case someone wanted a custom value.
I think the current implementation allows for you to create a DNS record with a TLL in the Netlify dashboard and then when it is updated the TLL should be retained.