Release 0.2.2

Better handling of yarn install. In particular this occurs now before running react-native -v in order to get a meaningful report of the version of RN in use.

Added a Rake task:

require 'react_native_util/rake/react_pod_task'
ReactNativeUtil::Rake::ReactPodTask.new chdir: '/path/to/project'

There is also now an example app in this repo under examples/TestApp. Use rake react_pod to convert it. Use rake clobber:examples and git checkout -- . to clean up after the conversion without committing.