message: change all markets from Option<&str> to Option<Country>
diff: @@ -168,7 +168,7 @@ impl Spotify {
  ///Parameters:
  ///- track_ids - a list of spotify URIs, URLs or IDs
  ///- market - an ISO 3166-1 alpha-2 country code.
  - pub fn tracks(&self, track_ids: Vec<&str>, market: Option<&str>) -> Result<FullTracks> {
  + pub fn tracks(&self, track_ids: Vec<&str>, market: Option<Country>) -> Result<FullTracks> {
  let mut ids: Vec<String> = vec![];
  for track_id in track_ids {
  ids.push(self.get_id(Type::Track, track_id));
  @@ -177,7 +177,7 @@ impl Spotify {
  // url.push_str(&ids.join(","));
  let mut params: HashMap<String, String> = HashMap::new();
  if let Some(_market) = market {
  - params.insert("market".to_owned(), _market.to_owned());
  + params.insert("market".to_owned(), _market.as_str().to_owned());
  }
  println!("{:?}", &url);
  let result = self.get(&url, &mut params);
  @@ -554,13 +554,13 @@ impl Spotify {
  fields: Option<&str>,
  limit: L,
  offset: O,
  - market: Option<&str>)
  + market: Option<Country>)
  -> Result<Page<PlaylistTrack>> {
  let mut params = HashMap::new();
  params.insert("limit".to_owned(), limit.into().unwrap_or(50).to_string());
  params.insert("offset".to_owned(), offset.into().unwrap_or(0).to_string());
  if let Some(_market) = market {
  - params.insert("market".to_owned(), _market.to_owned());
  + params.insert("market".to_owned(), _market.as_str().to_owned());
  }
  if let Some(_fields) = fields {
  params.insert("fields".to_owned(), _fields.to_string());
  