Add Support for Delete Rubric

[fredpyo]

What resource needs additional coverage? Rubrics

What endpoints need to be covered? DELETE /api/v1/courses/:course_id/rubrics/:id Docs here: https://canvas.instructure.com/doc/api/rubrics.html#method.rubrics.destroy

I looked around the code but I couldn't find this particular call, only references to deleting the rubric associations. Hopefully this bug report is OK.

[ggarfink]

I'd be willing to work on this issue. Any other information I should have before I start working on it?

[Thetwam]

Hey @ggarfink, thanks for volunteering! Check out the Contributing Guide to get started. If you have any questions at all, feel free to post here.

We're also on the UCF Open Source Slack in the #canvasapi and #canvasapi-dev channels for more immediate contact.

Thanks again!

[Thetwam]

Resolved in #485