Don't include customer_number unless it is numeric.
Don't include customer id unless it is numeric.
Accept numeric strings as well.
Add tests for excluding customer_number for non numeric values.
Merge pull request #703 from Shopify/sagepay-fix

Sage Payments: Don't include customer_number unless it is numeric.
Add tests for authnet cust_id fix.
Merge pull request #704 from Shopify/authnet-email-fix

Don't include customer id unless it is numeric.