Updated the Heroku Sinatra sample app so it will run on Heroku

[hkp]

I added a Gemfile and Gemfile.lock so folks can run this sample and it'll just work. I opened an issue and then decided to send a fix so you guys could do more important stuff. ;)

[tommay]

Thanks for actually making this work on heroku. You'd think they'd pull this.

[ghost]

Lets get this pulled in, please.

[fossil12]

+1 the current master of this repo doesn't work anymore...