news/category?{category_id}
Retrieves all news within a given category.
Arguments:
- api_key (required)
 - per_page (optional - default 10)
 - page (optional - default 1)
 - category_id (required)
 
Example request:
http://[domain]/api/news/category.xml?api_key=[api_key]&category_id=20000
Example response:
<?xml version="1.0" encoding="utf-8"?>
<newsItems category_id="20000" page="1" pages="1" per_page="10" total="1">
    <news id="2">
        <title>3D printed moon building designs revealed</title>
        <summary>The architects behind...</summary>
        <content><![CDATA[<p>An inflatable structure ...]]></content>
        <imageURL></imageURL>
        <newsDate>1359729360</newsDate>
        <categories>
                <category id="20000" name="Category One"/>
        </categories>
    </news>
</newsItems>