Move proration date to subscription update
Move proration date to subscription update

Originally the proration date got appended to the body of the POST request to create a subscription,
which makes no sense at all.

What we really need, is to add the proration date on the update call.

dominicphillips/stripe-go,collinglass/stripe-go,shazow/stripe-go,BearchInc/stripe-go,ChannelMeter/stripe-go,froatsnook/stripe-go,ChannelMeter/stripe-go,stripe/stripe-go,hyperworks/stripe-go,froatsnook/stripe-go,mondough/stripe-go,stripe/stripe-go,mondough/stripe-go,dominicphillips/stripe-go