Extended framework with infrastructure of pluggable json and xml serializers. Decoupled controller factory and composition root. Used json.net library as plugin for framework in order to show how it can be extended. Implemented different response format based on requests's content-type header. Implemented default xml and json serializers. Added comments.
Changed storage system from csv to database. Implemented repositories and unit of work in data access layer. Changed business logic, removed redundant classes. Added mapper to bll.