resolve $13.19 discrepancy with Balanced

[chadwhitacre]

Reticketed from #308 (comment) since that ticket is big and noisy. The purpose of this ticket is to reconcile the information in Balanced with the information we have in Xero.

[chadwhitacre]

One place we're at with this is that we haven't found a way to compute our Balanced dashboard balance from either an export or the JSON API.

Source	Balance ($)	∆ ($)
Balanced dashboard	28,402.62	0
transactions/*.json	28,389.43	-13.19	script
invoices + transfers	27,632.58	-770.04	script

[chadwhitacre]

cc: @msherry I've split off a ticket about reconciling with Balanced to avoid subjecting you to the noise of the other ticket. :-)

[chadwhitacre]

Source	Balance ($)	∆ ($)
payments export	154,059.83	+125,657.21	script

[chadwhitacre]

Over on #308, we ended up reconciling with Balanced by computing monthly statements from transactions.json.

[chadwhitacre]

... so we are out $13.19 from the Balanced dashboard. We are reconciled with our marketplace bank account, but not yet with the Gratipay db.

[chadwhitacre]

Closing to keep this repo clean. Will be sussed out under gratipay/finances#3.