Issue with Cybersource subscription amount: `money_format = :cents'

Cybersource subscription amount were not being converted to dollars in soap envelope. 

### Example:

```ruby
{
  :setup_fee => 1000,
  # (...)
  :subscription => {
    # (...)
    :amount => 1000
  }
}
```
generating a request with a wrong amount
```xml
<purchaseTotals>
  <currency>USD</currency>
  <grandTotalAmount>10.00</grandTotalAmount>
</purchaseTotals>
<!-- (...) -->
<recurringSubscriptionInfo>
  <amount>1000</amount>
  <!-- (...) -->
</recurringSubscriptionInfo>
```

Subscription created with `$1,000.00` instead of `$10.00`