lib/cookie.js
function clear(except, options) {
  var keys = this.get(), z;
  except = except || [];
  for(z in keys) {
    if(~except.indexOf(z)) {
      continue;
    }
    this.del(z, options);
  }
}
function clear(except, options) {
  var keys = this.get(), z;
  except = except || [];
  for(z in keys) {
    if(~except.indexOf(z)) {
      continue;
    }
    this.del(z, options);
  }
}
Clear all stored cookies, optionally keeping the
keys in the except array.

@param except Array of keys that should not be deleted.
@param options The cookie options.