Paying for Product and Feature Credits via Stripe

![screen shot 2014-04-23 at 9 16 46 pm](https://cloud.githubusercontent.com/assets/716573/2785214/073fbf7c-cb4f-11e3-9a80-626d42d368a2.png)
![screen shot 2014-04-23 at 9 16 58 pm](https://cloud.githubusercontent.com/assets/716573/2785215/07408678-cb4f-11e3-987e-2202070d74bc.png)
![screen shot 2014-04-23 at 9 17 05 pm](https://cloud.githubusercontent.com/assets/716573/2785216/07412dbc-cb4f-11e3-8bbb-5c7928bf7ac6.png)