this adds a client method to retrieve a collection post along with basic
tests - phabricator task T588

This reverts commit 1d34eede72.

for creating a new collection.

Rather than accepting a naked string, accept a DeleteCollectionParams
struct so that new optional parameters can be added in the future
without breaking the API.

This adds support for deleting collections.

Resolves #1.

This closes #3

writeas.github.io/docs -> developer.write.as/docs/api

Includes ability to make authenticated requests and get posts.