create class rating and create association
create method crete_rating

Signed-off-by: Murilo Duarte <muriloduartegoncalves@hotmail.com>
Signed-off-by: Karine Valença <valenca.karine@gmail.com>
Merge branch 'development' of https://github.com/muriloduarte/TEM-DF into development

Conflicts:
	app/controllers/medics_controller.rb
	app/models/rating.rb
	db/migrate/20141022141120_create_ratings.rb
	db/schema.rb