added purchase link to readme file.

git-svn-id: https://plugins.svn.wordpress.org/etsy360/trunk@957332 b8457f37-d9ea-0310-8a92-e5e31aec5664
added purchase link to readme file.

git-svn-id: https://plugins.svn.wordpress.org/etsy360/trunk@957336 b8457f37-d9ea-0310-8a92-e5e31aec5664