lib/cookie.js
function del(key, options) {
  if(!options) {
    options = {};
    for(var z in this.options) {
      options[z] = this.options[z];
    }
  }
  options.expires = -1;
  this.set(key, '', options);
}
function del(key, options) {
  if(!options) {
    options = {};
    for(var z in this.options) {
      options[z] = this.options[z];
    }
  }
  options.expires = -1;
  this.set(key, '', options);
}
Delete a cookie value.

@param key The cookie key name.