BECS support

[joannasese]

Completed:

• Added bsb_code field
• Included test

Affects the following endpoints:

• PUT /v2/accounts/{account_id}/billing_info
• PUT /v2/accounts/{account_id}
• POST /v2/accounts
• POST /v2/purchases
• POST /v2/purchases/preview
• POST /v2/subscriptions

To create billing_info with BECS:

$billingInfo = new Recurly_BillingInfo();
$billingInfo->account_code       = $accountCode;
$billingInfo->address1           = '123 Paper Street';
$billingInfo->city               = 'Adelaide';
$billingInfo->zip                = 'W1K 6AH';
$billingInfo->country            = 'AU';
$billingInfo->phone              = '213-555-5555';
$billingInfo->name_on_account    = 'BECS account name';
$billingInfo->account_number     = '11223311';
$billingInfo->bsb_code           = '082-082';
$billingInfo->type               = 'becs';
$billingInfo->create();