The Getting Started edit and create posts examples are incorrect

The `updated-post.json` from the Editing Posts example is re-used in the Create Posts example.  That should be changed since there are required parameters when creating a post.  Also the `modified` parameter is no longer available when creating OR editing a post.

In summary:

- [x]  Update new post example to include `content_raw` as a parameter.
- [x]  Change new and edit posts examples to use `date` parameter instead of `modified` parameter.