Update model naming for arrays and refactor

[Manfred]

• Changes model naming so the model name for a collection doesn't conflict with its items.

An array could previously get the same model name as its items and that would result in an exception TypeError: no implicit conversion of Hash into Integer because we would attempt to initialize an Array subclass with a Hash of attributes.

This PR changes the logic to add Collection to the array model name, eg. BooksCollection so it doesn't conflict with the item model name, eg. Book.

References #52.