updated readme.txt

git-svn-id: https://plugins.svn.wordpress.org/simple-facebook-pixel/trunk@994677 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated name

git-svn-id: https://plugins.svn.wordpress.org/simple-facebook-pixel/trunk@994682 b8457f37-d9ea-0310-8a92-e5e31aec5664