yard should be a runtime dep. so users can host docs locally
should have a rake tasks for building docs
yardoc should have readme
code blocks should be indented 2 spaces
yard should not be a runtime dependency

I am not sure what I was thinking, but it is not possible to build the
docs without the source code.

-1 to @jmoody
Merge pull request #398 from calabash/feature/add-yard-doc-support

Feature/add yard doc support