Fix BitPay Helper to use form_fields for generating invoice id
Fix BitPay Notification status
Implement BitPayNotification#acknowledge to request invoice
BitPay Notification#gross should return price, not btcPrice
parse posData as JSON string, and handle JSON ParseErrors
Fix incorrect notification definition which should allow for options to be passed
Fix status mapping
Merge pull request #908 from Shopify/fix_bitpay

Fix BitPay implementation