updated plugin icon and tested-up-to for 4.0

git-svn-id: https://plugins.svn.wordpress.org/mobile-smart/trunk@978850 b8457f37-d9ea-0310-8a92-e5e31aec5664
bug fix for switch for tablets, and updated readme.txt

git-svn-id: https://plugins.svn.wordpress.org/mobile-smart/trunk@978863 b8457f37-d9ea-0310-8a92-e5e31aec5664
add banner image

git-svn-id: https://plugins.svn.wordpress.org/mobile-smart/trunk@978889 b8457f37-d9ea-0310-8a92-e5e31aec5664