CONTRIBUTING.md: Add development section
CONTRIBUTING.md: Add development section

soupmatt/rails_admin,zambot/rails_admin,sferik/rails_admin,widgetworks/rails_admin,dalpo/rails_admin,soupmatt/rails_admin,dalpo/rails_admin,widgetworks/rails_admin,zambot/rails_admin,sferik/rails_admin,zambot/rails_admin,dalpo/rails_admin,sferik/rails_admin,widgetworks/rails_admin,soupmatt/rails_admin