Hh review

Hey Nick,

Good job.  This is mostly right, with a few issues:

**Need a `UserTaskList` join table.** The main one is that you should have a join table between `User` and `TaskList`, since it's a many-to-many relationship:  a `User` can have many `TaskList`s, and a `TaskList` can have many `User`s.  The `has_and_belongs_to_many` is kind of a way around this, but it's deprecated and the better practice is to create a join table and set up your associations like so:

```ruby
# migration to create the join table
class CreateUserTaskLists < ActiveRecord::Migration
  def change
    create_table :user_task_lists do |t|
      t.integer :user_id, null: false
      t.integer :task_list_id, null: false

      t.timestamps
    end
  end
end
```
```ruby
# app/models/user_task_list.rb
class UserTaskList < ActiveRecord::Base
  belongs_to :user
  belongs_to :task_list
end
```
```ruby
# app/models/task_list.rb
class TaskList < ActiveRecord::Base
  has_many :user_task_lists
  has_many :users, through: :user_task_lists

  # ...
end
```

```ruby
# app/models/user.rb
class User < ActiveRecord::Base
  # instead of has_and_belongs_to_many, use a join table with a has_many through association
  has_many :user_task_lists
  has_many :task_lists, through: :user_task_lists

  # ...
end
```