Update gems with `bundle update`.
Update gems with `bundle update`.

Bump up to latest of all of them.

Tested:
$ bundle exec rspec
$ bundle exec rubocop

Also ran the website locally and pushed to vimgolf-staging on Heroku.

igrigorik/vimgolf,igrigorik/vimgolf,igrigorik/vimgolf,igrigorik/vimgolf