Fixed duplicate class declaration in the API

git-svn-id: https://plugins.svn.wordpress.org/datafeedr-api/trunk@857360 b8457f37-d9ea-0310-8a92-e5e31aec5664
Added if(!class_exists('...')) checks to the Datafeedr Api Client Library.

git-svn-id: https://plugins.svn.wordpress.org/datafeedr-api/trunk@858015 b8457f37-d9ea-0310-8a92-e5e31aec5664