Update readme with correct versions

git-svn-id: https://plugins.svn.wordpress.org/instamojo/trunk@887857 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fix tested upto version

git-svn-id: https://plugins.svn.wordpress.org/instamojo/trunk@887858 b8457f37-d9ea-0310-8a92-e5e31aec5664
Add changelog

git-svn-id: https://plugins.svn.wordpress.org/instamojo/trunk@887860 b8457f37-d9ea-0310-8a92-e5e31aec5664