update the competition forms

some of the updates I made when styling the competition show page
affected the layout of the whole site, so the competition form pages
needed to be updated. I also made the submit buttons looks more
consistent with the rest of the site.
add a callback to close connections to the db

apparently Sinatra doesn't handle this automatically, at least for
Postgres. I'm not 100% sure this is a good solution but I'll keep it if
it works.