Add mechanism to block until page created

[SamWhited]

Overview

When creating a new page with the API, and then attempting to pin it, pinning fails because the new post isn't yet created. It sometimes takes a few seconds after the request to create the page has returned before the page actually exists.
It would be nice if the API either blocked and only returned the request when the post actually existed and could be manipulated, or if there was a mechanism to wait until a post existed (short of polling in a loop and hammering your servers until we get a page back).

I couldn't find any documentation that mentioned that page creation was eventually consistent, so if this is unintentional consider this a bug report instead of a feature request.

[SamWhited]

I can't reproduce this today, despite the fact that it was happening when I first wrote (but forgot to submit) this issue a few days ago. Going back to try and figure this out and will reopen if it's actually a problem.