Gaps left by #intersection

[jhovad]

It would be very helpful to have complementary method to #intersection ... like here:
https://github.com/rossmeissl/timeframe/blob/2cd85dd2a3ec2fbdf5391bf49870d6fd27265bd7/lib/timeframe.rb#L260

For example: I have general availability of the resource and Clients can book this resource. Then I would like to display availability that left after this bookings. There I need something like
current_availability = general_availability.gaps_left_by(bookings)

[arnau]

Hi @jhovad, the idea worth having a look but I'm not likely to have time any time soon. I'm happy to review any PR implementing it 👍