Add examples and extensions for other DALs and ORMs

[mwpastore]

• Relational Databases
  • ActiveRecord
• Non-Relational Databases
  • Mongo

Guidelines:

1. Hard-fork sinja-sequel.
2. Rename the project and update the gemspec and file and directory names:
   • sinja-sequel.gemspec
   • lib/sinja-sequel.rb
   • lib/sinja/sequel.rb
   • lib/sinja/sequel/
   • lib/sinatra/jsonapi/sequel.rb
3. Minimally, update core.rb to provide the basic configuration and helpers for the library in question:
   • Configuration
     • conflict_exceptions
     • not_found_exceptions
     • validation_exceptions
     • validation_formatter
   • Helpers
     • transaction
     • filter
     • sort
     • finalize
     • validate!
4. If the library supports pagination, update pagination.rb (and its hook in core.rb):
   • Configuration
     • page_using
   • Helpers
     • page
5. Add helpers to helpers.rb that will ease the pain of writing action helpers, if any.
6. Rewrite the extension to generate basic action helpers for resource, has_many, and has_one, if possible.
7. For bonus credit, import/fork the demo app and port it to your new extension.
8. Update README.md to reflect your work and document best practices.
9. Send me a PR to add your extension to the main Sinja README (pending a code review).
   • Alternatively, pending a code review, I would be willing to fork your repo and assume maintainership of the extension, adding you back as a contributor.