code: function Client(options) {
    EventEmitter.call(this);
  
    var defaults = this.constructor.defaults;
  
    this.options = extend({}, defaults, options);
    this.options.headers =
      extend({}, defaults.headers, options && options.headers);
  
    this.state = new ClientState(this);
    this.messages = [];
  }
docs: @module zotero 
  Creates a Zotero Client instance. A Client manages HTTPS connections
  to Zotero API servers.
  
  @class Client
  @constructor
  @extends EventEmitter
  
  @param {Object} options - override the default configuration.