actions need yarddoc

## motivation

The calabash _actions_ (e.g. touch, double_tap, swipe, pan, etc) are not exposed anywhere in the public API.

I created a Calabash::Cucumber::Actions module that stubs these methods.  This module is for documentation purposes only.

## todo

- [ ] @krukow Can you finish the documentation?  I did what I could, but I don't know how document the `options` argument.

UPDATE:  This is ready to merge, but if you want to finish the docs on this branch you can add commits to this pull request.