create new table likes
add likes_count to use for counter cache
setup associations among users, slides and likes
not to use turbolink on slide pages
introduce noty
make query.noty to work
new route entries for like and collect slides
likes should be unique on user and slide
a new method to determine if a user has liked on a slide
slides like action implementation
update the authenticate_user! method to work with xhr request
handle like slide button
update the link to like slide
create collections table to prepare for storing collect records
update the link to collect slides
setup associations among users, slides and collections
add a new filed name `collections_count` to use as a counter_cache
new method to determine if a user has collected a slide
update the link to collect slide
enable to record collection