Fixed z-index issue with menu top position. 

git-svn-id: https://plugins.svn.wordpress.org/wp-responsive-menu/trunk@968236 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fixed top menu position issue with other elements and updated readme. 

git-svn-id: https://plugins.svn.wordpress.org/wp-responsive-menu/trunk@968237 b8457f37-d9ea-0310-8a92-e5e31aec5664