v0.2.2

• Messages generated by tbl_grade_class() now internally call two generic S4 functions:
  • friendly_class() generates class names for single objects.
    • e.g. friendly_class(character(1)) returns "a text string (class character)".
  • hinted_class_message() generates messages when object and expected are both a specific class.
    • e.g. if object is an ungrouped tibble and expected is a grouped tibble, hinted_class_message() generates a message that suggests using group_by().
  • Using generic functions allows tbl_grade_class() messages to be expanded by adding methods for new classes in tutorial setup code or external packages.