message: Actually set the Stripe-Account header when needed
diff: @@ -97,6 +97,9 @@ impl Client {
  let mut headers = Headers::new();
  headers.set(Authorization(Basic{username: self.secret_key.clone(), password: None}));
  headers.set(ContentType::form_url_encoded());
  + if let Some(ref account) = self.params.stripe_account {
  + headers.set_raw("Stripe-Account", vec![account.as_bytes().to_vec()]);
  + }
  headers
  }
  }
  