Remove old version of leafletjs, update readmes (now tested in 3.8.1), remove code for IE conditional css

git-svn-id: https://plugins.svn.wordpress.org/advanced-custom-fields-leaflet-field/trunk@854980 b8457f37-d9ea-0310-8a92-e5e31aec5664
Added leaflet 0.7.2

git-svn-id: https://plugins.svn.wordpress.org/advanced-custom-fields-leaflet-field/trunk@854982 b8457f37-d9ea-0310-8a92-e5e31aec5664