Sinatra/mongoid issues

app.rb

#removed a bunch of routes that aren't relevant

require 'rubygems'
require 'bundler'

require 'sinatra'
require 'haml'
require 'bson'

require 'models/user'
require 'models/monger'
#require 'models/location' 
#require 'models/review'
require 'mongoid'
require 'yajl'
require 'oa-oauth'

class Burritowar < Sinatra::Base  
  set :app_file, __FILE__
  set :root, File.dirname(__FILE__)
  set :server, 'thin'

  Mongoid.configure do |config|
    host = "localhost"
    config.master = Mongo::Connection.new.db("burritowar")
  end

  get '/auth/:provider/callback' do    
    auth = request.env['omniauth.auth']
    time = Time.now.to_i


    #following line produces this error: "ArgumentError - wrong number of arguments (1 for 0):"
    user = User.new( :name => 'what', :nickname => 'what', :provider => 'twitter', :provider_id => 'what', :last_update => 'never' )
    user.save
    
    session[:uid] = auth['uid']
    session[:name] = auth['user_info']['nickname']
    
    if session[:redirect]
      redirect session[:redirect]
      session.delete('redirect')
    else
      redirect '/'
    end
  end
end

user.rb

require 'mongoid'

class User
  include Mongoid::Document
  field :name, :type => String
  field :nickname, :type => String
  field :provider, :type => String
  field :provider_id, :type => String
  field :last_update, :type => String
  #references_many :reviews, :stored_as => 'hash'
end