Add Role.delete_role_delete_stories

Method for deleting a Role and its related User Stories

closes #1
Refactor: Move role and role_id to RoleTest.setUp
Add Role.delete_role_reassign_all_stories

Method for deleting a Role and reassigning its related User Stories to
a single existing Role.

closes #2
Bugfix: delete_role_reassign_all_stories

Indention typo was causing failing test to pass. The typo has been
fixed, and the code has been updated so that the test now passes.
Add Role.delete_role_reassign_individual_stories

Method for deleting a Role and reassigning its related User Stories to
various other existing Roles.

closes #3