Don't show class .void when no failed payments

Addresses issues from https://github.com/spree/spree/issues/4260

Not ready for merge yet.

- [ ] `Order#is_risky?` is used in `app/views/spree/admin/orders/_risk_analysis.html.erb` partial, when it really should be checking if  `Order.payments.failed.count > 0`. As a result, when orders have 1 or more payments that have not been accepted, `Failed Payment Attempts` uses css class `.void` (a red circle) instead of CSS class `.complete` (a green circle).
- [ ] Fixing the previous bug removes the only place `Order#is_risky?` was used, but this method may still be useful. 
- [ ] A certain CVV response is displaying an error when it should not.

![screen shot 2014-01-27 at 10 03 11 pm](https://f.cloud.github.com/assets/199422/2016630/e30d2f96-87e1-11e3-8a9a-e7edfba1e6b8.png)