Add usage to readme

[npentrel]

I've been looking for about 15 minutes now after discovering a Pipfile in a project I was looking at. I can't figure out how to use it. Maybe you could add a simple example usage to your readme?

[timofurrer]

This repository is just about the specification of the Pipfile.
You want to have a look at: https://github.com/kennethreitz/pipenv

It's the only tool at the moment which can handle Pipfiles.
In the future pip should also be able to handle Pipfiles as described here: https://github.com/pypa/pipfile#pip-integration-eventual

[kennethreitz]

Thanks, @timofurrer