Add Recipe 0014 and add add_item() to AccompanyingCanvas

[markpbaggett]

What does this do?

1. This adds a solution for Recipe 0014.
2. Attempts to address Issue 199 by making add_item() available to AccompanyingCanvas.
3. Adds a test to check that members of items in AccompanyingCanvas are AnnotationPages when added with add_item().

[glenrobson]

Sorry to be a pain @markpbaggett but would it be possible to implement the baseurl like Mike has done in the following pull request:

https://github.com/iiif-prezi/iiif-prezi3/pull/183/files

it will make the recipes more consistent and I'm hoping another push might allow me to approve the workflows to run now you are apart of the github team.

[markpbaggett]

@glenrobson, not a pain at all! I'm happy to do it and think this will look much better. I'll work on this tonight.

[markpbaggett]

@glenrobson, I've added the base_url pattern here.

[glenrobson]

Great thanks! All the checks ran as well this time.