WIP Prepare the gem for yard (documentation engine)

**WIP** This needs careful review and probably some changes before it is merged.

These PR should be resolved before merging this one.

* https://github.com/calabash/calabash-android/pull/468
* https://github.com/calabash/calabash-android/pull/469
* https://github.com/calabash/calabash-android/pull/470