add CRUD/assign methods for tags to recipes
add assign function for tags; add validation on tag creation
add list of tags to recipes#show view and vice versa
make 'remove' function for removing tags from recipes and vice versa
create a rating class
add method to assign ratings to recipes
add function to remove rating from recipe
add functionality to display favorite recipes
modify index view for favorites
fix ratings feature to allow multiple ratings
re-fix the ratings feature/sorting on index view