Mention PUT in suggested response status codes

Also fixed a small typo for 200 / GET status code description.  
@geemus,

So, I'd see two main uses cases for `PUT`:
1. As an alternative to `POST` to create a new resource, in cases where the primary key is provided by the client rather than generated by the server (so you'd `PUT /some-resources/primary-key`, but you'd `POST /some-resources`).
2. As an alternative to `PATCH` that replaces the entire resource instead of partially `PATCH`-ing it.

Now, I think the response code shouldn't depend on the use case, but should instead depend on what the server actually did. 

According to 9.6 here http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html — 201 should indeed be returned to indicate a resource was created, and 200 if it was modified (or 204 if no content is returned, but that'd be incompatible with the "Provide full resources where available" guideline here).

I'll update the PR.