Key's Value for boolean method?, should be boolean type

Currently the method [column_methods_hash](https://github.com/rails/rails/blob/master/activerecord/lib/active_record/model_schema.rb#L259) return this. eg

```
2.0.0p195 :004 > Account.column_methods_hash
 => {:id=>id, :id==>id, :id?=>id, :id_before_type_cast=>id, :name=>name, :name==>name, :name?=>name, :name_before_type_cast=>name, :user_id=>user_id, :user_id==>user_id, :user_id?=>user_id, :user_id_before_type_cast=>user_id, :created_at=>created_at, :created_at==>created_at, :created_at?=>created_at, :created_at_before_type_cast=>created_at, :updated_at=>updated_at, :updated_at==>updated_at, :updated_at?=>updated_at, :updated_at_before_type_cast=>updated_at}
```

```
2.0.0p195 :010 > Account.first.user_id?
Account Load (0.3ms)  SELECT accounts.* FROM accounts ORDER BY accounts.id ASC LIMIT 1
=> true
```
**The above is a boolean return. For boolean method**

```
2.0.0p195 :014 > Account.first.name
Account Load (0.2ms)  SELECT accounts.* FROM accounts ORDER BY accounts.id ASC LIMIT 1
=> Ankit
```

**The above return it's value/type of method name**

The correct return from the method [column_methods_hash](https://github.com/rails/rails/blob/master/activerecord/lib/active_record/model_schema.rb#L259) should include boolean for boolean methods

```
 => {:id=>id, :id==>id, :id?=>boolean, :id_before_type_cast=>id, :name=>name, :name==>name, :name?=>boolean, :name_before_type_cast=>name, :user_id=>user_id, :user_id==>user_id, :user_id?=>boolean, :user_id_before_type_cast=>user_id, :created_at=>created_at, :created_at==>created_at, :created_at?=>boolean, :created_at_before_type_cast=>created_at, :updated_at=>updated_at, :updated_at==>updated_at, :updated_at?=>boolean, :updated_at_before_type_cast=>updated_at}
```