The Getting Started edit and create posts examples are incorrect

[rachelbaker]

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:

• Update new post example to include content_raw as a parameter.
• Change new and edit posts examples to use date parameter instead of modified parameter.

[rachelbaker]

@rmccue #reviewmerge