Update factory girl.

[#66380498]
Include FactoryGirl in spec_helper.

[#66380498]
Fix a typo in response notification spec.

[#66380498]
Define factories to be used in prediction and notification specs.

[#66380498]
1. Update prediction model and controller to handle scenarios when
predictions do not have parameter "private".

2. Move prediction privacy specs from model specs to controller specs
and update other related specs.

[#66380498]
Reduce memory consumption of sending notification emails by applying
find_each, and update related specs.

[#66380498]
Merge branch 'reduce_email_notification_memory_use_#66380498'