Ning API Documenation now available as PDF download

[Devin]

A PDF download is now available for the Ning API documentation. You'll find a link at the top of table of contents to download the PDF.

There is a known issue where the longer code samples run off the edge of the page. You can still copy and paste the hidden text. I'm still searching for a solution that will insert the necessary line breaks automatically.

I've also updated the PHP client library example to match the changes Ben made to the library.