To deploy:
$ cf push
Using manifest file manifest.yml
Custom startup command> none
Creating hello... OK
1: hello
2: none
Subdomain> hello
1: mypaas.com
2: none
Domain> mypaas.com
Binding hello.mypaas.com to hello... OK
Uploading hello... OK
Starting hello... OK
-----> Downloaded app package (4.0K)
Installing ruby.
-----> Using Ruby version: ruby-1.9.2
-----> Installing dependencies using Bundler version 1.3.2
Running: bundle install --without development:test --path vendor/bundle --binstubs vendor/bundle/bin --deployment
Fetching gem metadata from https://rubygems.org/..........
Installing rack (1.5.2)
Using bundler (1.3.2)
Your bundle is complete! It was installed into ./vendor/bundle
Cleaning up the bundler cache.
-----> Uploading staged droplet (24M)
-----> Uploaded droplet
Checking hello...
Staging in progress...
0/1 instances: 1 starting
0/1 instances: 1 starting
1/1 instances: 1 running
OK
$ curl hello.mypaas.com
Hello World!