Add JRuby Support in rails3 and sinatra staging plugin

Add JRuby Support in rails3 and sinatra staging plugin.

This pull request is based on the contribution (pull request) of tarcieri.

https://github.com/cloudfoundry/vcap/pull/24

Last month, By chance I found this pull request.
I was very interested, and tried this feature on my VCAP.

Simple app such as Sinatra trivial app, was easy to working,
but Slightly more complex apps such was not working at all.

I was struggling with this problems, made the following fixes and improvements.

- Fix the mismatch gem install path that GemfileTask#install_gems method installed and Bundler search path. 
  this fix is also necessary for other Ruby runtime (Ribinius, REE)
- Correct JRuby C Extension on ubuntu (for thin server)
- Make sample apps for test connectivity to current available services and servers. some of apps is put into vcap-test-assets.
- Make specs for vcap-tests.

My JRuby on CloudFoundry sample apps are available on following link.

https://github.com/schinen/jruby-cloudfoundry-samples

Apps is truly trivial, such as one model and one attribute scaffolding app for test connectivity to services.

I'm really a beginner in Ruby, all inputs are welcome.

Thanks.
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