[Codemod / Fragments] handle baseFragment details correctly

[richgt]

The latest codemod that has been merged into @wagenet's branch handles individual Fragment files, including files that extend a BaseFragment class. However, we're not reading the baseFragment itself to create the traits / etc that need to be added to the fragment.

We need to add logic to read the base fragment class and create traits and whatever else is necessary to append to the existing models / fragments.