Updated routes to include AccountsController.

  Allow Recurly to access the POST url necessary to show the success page.
Configured Recurly to use a proper signature.

  As per the documentation found in http://docs.recurly.com/recurlyjs, ensure
  that Rails generate a proper signature. Also set a URL that the routes would
  use to redirect to.
Updated Recurly configuration.

  Allow staging configuration options if we're not in production mode.