opposed to the available options as a comment perhaps better to link to either churn documentation or to code using all the available options.

* Sadly the documentation covers the cmd line usage but doesn't cover direct lib access or I could add this but no where good to link in the docs at the moment.
* other option is linking to code which uses all available options. Where I parse cmd line into the [options hash](https://github.com/danmayer/churn/blob/master/bin/churn#L66)

Let me know which you think is best and I can switch this up.