message: Add missing params to InvoiceListParams
diff: use error::Error;
  use client::Client;
  -use params::{List, Metadata, Timestamp};
  +use params::{List, Metadata, RangeQuery, Timestamp};
  use resources::{Currency, Discount, Plan};
  use serde_qs as qs;
  @@ -130,10 +130,18 @@ pub struct Invoice {
  #[derive(Default, Serialize)]
  pub struct InvoiceListParams<'a> {
  + #[serde(skip_serializing_if = "Option::is_none")]
  + pub customer: Option<&'a str>,
  + #[serde(skip_serializing_if = "Option::is_none")]
  + pub date: Option<RangeQuery<Timestamp>>,
  + #[serde(skip_serializing_if = "Option::is_none")]
  + pub ending_before: Option<&'a str>,
  #[serde(skip_serializing_if = "Option::is_none")]
  pub limit: Option<u64>,
  #[serde(skip_serializing_if = "Option::is_none")]
  - pub customer: Option<&'a str>,
  + pub starting_after: Option<&'a str>,
  + #[serde(skip_serializing_if = "Option::is_none")]
  + pub subscription: Option<&'a str>,
  }
  impl Invoice {
  @@ -175,7 +183,7 @@ impl Invoice {
  client.post(&format!("/invoices/{}", invoice_id), &params)
  }
  - /// Lists all invoices with optional customer_id and limit params
  + /// Lists all invoices.
  ///
  /// For more details see https://stripe.com/docs/api#list_invoices.
  pub fn list(client: &Client, params: InvoiceListParams) -> Result<List<Invoice>, Error> {
  