tests were failing on expected write.as blog title
previously the title was 'write.as' and it is now 'write.as blog'

also removed test case ExampleClient_GetCollection as was a duplicate of
TestGetCollection

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

This reverts commit 1d34eede72.

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