Update all things jQuery

This issue ensures that the jQuery Gem must use a version equal to ```4.0.0``` or higher. The jQuery validates plugin has also been updated. It seems however that the jQuery UI JavaScript and CSS files contained in ```/vendor/assets/``` are up to date.

This issue fixes #86.

Thankyou for creating this website!
psgs :palm_tree:
`jquery-rails` 4 isn't compatible with Rails 3. I've updated the app to the latest compatible release of the gem @ #89. For further updates we need to first update the rails dependency here.