Add 'liked' class to product once the like icon is clicked

* Returning false inside an event callback has the same effect as calling e.preventDefault() - for not reloading the page - and e.stopPropagation() - for preventing it from flipping
Keep Heart state when product is liked
Prevent like-dislike-wrapper from flickering after like
CSS overrides for 900px wide medias
Move application css into main.css; change some navbar selectors
* Created separate 500px media query file for mobile responsiveness