Form submission should save number fields as numbers in JSON

[timwis]

In order for this event handler to work, cost's type must be an integer.

if data.cost >= 500:
    change_state('Awaiting CFO Approval')

Which means the form data grabber should recongise the <input type="number"> and save it as a number. This is like the one time when JavaScript is easier :P I assume there's no way to enable loose typing in event handlers, @mjumbewu, but worth asking..

[timwis]

Submitted PR to make this automatic at insin/get-form-data#7