Adding some more info to readme.txt so users could use it more efficiently.

git-svn-id: https://plugins.svn.wordpress.org/magic-wp-coupons/trunk@1033501 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme file changes

git-svn-id: https://plugins.svn.wordpress.org/magic-wp-coupons/trunk@1033503 b8457f37-d9ea-0310-8a92-e5e31aec5664