code: function SpotifySearch (title) {
    /**
     * @public {Array} tracks.
     */
    this.tracks = []
  
    // Query spotify, parse xml response, display in terminal,
    // prompt user for track number, play track.
    this._query(title)
    .then(this._parseJSON.bind(this))
    .then(this._printData.bind(this))
    .then(this._promptUser.bind(this))
    .then(this._playTrack.bind(this))
    .fail(this._onError.bind(this))
  }
docs: Spotify search client.
  @param {string} search query.
  @constructor