update readme.txt with new donation link

git-svn-id: https://plugins.svn.wordpress.org/svg-vector-icon-plugin/trunk@1007575 b8457f37-d9ea-0310-8a92-e5e31aec5664
fix tested up to in trunk/readme.txt

git-svn-id: https://plugins.svn.wordpress.org/svg-vector-icon-plugin/trunk@1007576 b8457f37-d9ea-0310-8a92-e5e31aec5664