Add section on unit testing
Implement ActiveDocument.find, move collection and client to class methods
Move ActiveDocument.find() to Persistence module
Red - First failing integration test for document.save
Implement document find() and save(), passing tests
Implement all_for_field() query functionality, pass tests
Tweak formatting
Implement tests for new_record? and persisted?. Temporarily denormalize Conversion methods to ActiveModel
Mark record as persisted after saving
Implement update()
Implement doc.destroy\!