title: ActiveModel::MissingAttributeError: can't write unknown attribute `user_id`?
body: <p>I've got a schema with leagues</p>
  
  <pre><code>  create_table "leagues", force: :cascade do |t|
      t.string   "name",                           null: false
      t.date     "start_date",                     null: false
      t.date     "end_date"
      t.string   "day"
      t.string   "start_time",                     null: false
      t.integer  "practice_length",                null: false
      t.integer  "alley_id",                       null: false
      t.integer  "frequency",                      null: false
      t.integer  "scratch",          default: 220
      t.integer  "handicap_percent", default: 80
      t.integer  "handicap_round",   default: 0
      t.integer  "occurrences",                    null: false
      t.integer  "user_id",                        null: false
      t.datetime "created_at",                     null: false
      t.datetime "updated_at",                     null: false
    end
  </code></pre>
  
  <p>and models</p>
  
  <pre><code>class Alley &lt; ActiveRecord::Base
    belongs_to :address
    has_many :leagues
  end
  
  class User &lt; ActiveRecord::Base
    has_many :leagues
  end
  
  class League &lt; ActiveRecord::Base
    belongs_to :alley
    belongs_to :user
    has_many :teams
  end
  </code></pre>
  
  <p>and factory</p>
  
  <pre><code>factory :league do
    name Faker::Company.name
    start_date start_date
    end_date end_date
    day Date.today.day
    start_time '7:00pm'
    practice_length 10
    frequency 1
    occurrences weeks
  
    association :alley, factory: :alley
    association :user, factory: :user
  end
  
  factory :user do
    email 'test@example.com'
    password 'Test1234'
    password_confirmation { 'Test1234' }
  end
  
  factory :alley do
    name Faker::Company.name
    association :address, factory: :address
  end
  </code></pre>
  
  <p>When I try to create a league, I get an error</p>
  
  <blockquote>
    <p>ActiveModel::MissingAttributeError:
       can't write unknown attribute <code>user_id</code></p>
  </blockquote>
  
  <p>It's set up exactly like alley, and alley works.  A league should be assigned to an alley and assigned to a user.  An alley can have many leagues and a user can have many leagues. Frankly, I'm too tired to figure out why this isn't working currently.</p>