Relation builder
relation => relations
Delegate all relation processing to relations.js
model#toJSON
Basic relation definitions (update is untested)
eliminate hasOne relations
Full tested relations updating and instantiation

TODO: hasMany
Functioning related collections implementation
test new merge
Simplify collection merging logic and delegate matching of new data to existing models to Model
toJSON for collections
normalize IDs on construction and split relations and data into two steps
Refactor relations
remove orphaned internal fn
add'l test coverage for model id
Merge branch 'cleanup' into relations
model#matches
Refactoring relations to use lazy eval (#11503960488350)
Refactor model to use new relations strategy

TODO: test #related
Transitioning to model.relations for relation methods — related objs can be POJOs on root model