Simplify chainable Resource.Promise promises

[eatyourgreens]

Use Array.map() to simplify the code that was generated by CoffeeScript 2.7 for Resource.Promise. This should make it easier to read (and follow?)

zooniverse/json-api-client#84 fixed zooniverse/Panoptes-Front-End#6380 and zooniverse/Panoptes-Front-End#6381 but the generated JavaScript is hard to read. This replaces it with a map of API resources => resource promises.

[eatyourgreens]

The original bug broke chained calls to client.type().get(), which returns an instance of Resource.Promise.

// get subjects for a subject set
apiClient
  .type('set_member_subjects')
  .get({ subject_set_id })
  .get('subject')
  .then(subjects => console.log(subjects));

// edit an existing Talk comment
talkClient
  .type('comments')
  .get({ id: commentId })
  .update(newComment)
  .save();

The fix involved declaring delete, get, save and update methods that all call the corresponding method on the original resource, which then allows resources to be chained.

[eatyourgreens]

Now that #192 is merged, this could also have some tests.

[mcbouslog]

LGTM, certainly more readable 👍 !

Tested locally with PFE installed with a package.json updated to "panoptes-client": "zooniverse/panoptes-javascript-client#chainable-resource-promise".

Locally I signed in/out, made a few classifications, in the lab I created a subject set and workflow ✅ .