Accounting for an inconsistency in 8tracks' API.

git-svn-id: https://plugins.svn.wordpress.org/8tracks-shortcode/trunk@897230 b8457f37-d9ea-0310-8a92-e5e31aec5664
Made sure the array values were unique when catsbuffer and tagsbuffer were merged...

git-svn-id: https://plugins.svn.wordpress.org/8tracks-shortcode/trunk@897236 b8457f37-d9ea-0310-8a92-e5e31aec5664