Moves default props out of react components and into objects

Instantiating a new BlogPost or Person gives a defaulted object back. To fill in the prismic data, you must call fetch and pass the ID of the object.
This allows blog post to have a default person for an author, so the react component can mount before the data is back from prismic.
Blog post component now only receives the post object. That object’s properties are used when rendering.
Renames BlogPost top level react component to root