Fixes the case when someone forks the repo and runs Travis on their own. Also, allows the use-case of restoring dependencies only without necessarily trying to cache them.
- Even after the cache is restored, `bundle install` still needs to hit RubyGems.org because there is no Gemfile.lock. There doesn't seem to be a way to tell it that everything it needs is right there in the `./bundle` directory. - Can't use `--standalone` due to bundler/bundler#2851 - It's not necessary to manually update RubyGems and Bundler anymore.
Failed because delta was 0.03097: https://travis-ci.org/lostisland/faraday/jobs/16672600
Fixes failing test in Rack adapter on Ruby 2.1.0