Default to installing gems on system

There are good reasons for vendoring gems for production deployments,
but in my experience, vendoring in development has given my teams more
trouble than the default behavior installing gems on the system.

Existing development environments will continue to use vendor/ until
they modify/remove .bundle/config, because these are mounted with the
source code. This will now slow docker image builds, since .dockerignore
now includes vendor/ and .bundle/.

bin/setup

@@ -17,7 +17,7 @@ fi
 
 # Set up Ruby dependencies via Bundler
 gem install bundler --conservative
-bundle check || bundle install --path=vendor/bundle
+bundle check || bundle install
 
 # Set up the database and add seed data
 bundle exec rake db:from_scratch