Photo change email notifications

Added email notifications whenever a personal or family photo is
changed.
Put spaces around operators, e.g. `if @id_key == 'family_id' or @id_key == 'person_id'`. Or better yet, use include, e.g. `if %w(family_id person_id).include?(@id_key)`.

https://github.com/bbatsov/ruby-style-guide