Add model definition comparing EmberData models with SchemaRecord#20

jaredgalanis merged 7 commits intoember-learn:mainember-learn/ember-data-request-service-cheat-sheet:mainfrom

MehulKChaudhari:add/model-schemaRecord-comparisonMehulKChaudhari/ember-data-request-service-cheat-sheet:add/model-schemaRecord-comparisonCopy head branch name to clipboard