Update ruby version for development
Add FactoryGirl integration

Introduce optional FactoryGirl syntax that makes it easier to use
Formulaic to fill in attributes from a factory with a single argument:
`fill_with_factory(:user)`; limit the attributes from a factory:
`fill_with_factory(:user, :name, :address)`; and even pass arguments to
the factory, such as traits and overrides:
`fill_with_factory(:user, :name, :address, factory_arguments: [:with_verified_address]`.

Resolves #11.
Clarify clarification
Remove brainstorm comments
The default in future versions will be true