Admin should be able to check history of previous payments of a user

[PatrikD]

There doesn't seem to be any way for an admin to check how much a user paid in previous months. And if the user just cancelled the payment plan, the admin dashboard won't even show their last payment either.

We may wind up having to pay hundreds of dollars to a former member, because (a) we were not able to cancel his membership when he asked us to (Issue #67 ), (b) he couldn't figure out how to cancel the recurring payment himself, (c) nobody ever gets notified whether or not anyone cancels their payment (Issue #53 ), and (d) we can't even check whether or not he actually paid what he said he paid!