CC-2950: Tell users if they are running an out-of-date version or not

1. changed the behavior so that the tooltip comes up on hover
2. changed stat server link to "http://stat.sourcefabric.org/airtime_latest_version"
3. only updates the db if version returned by stat server is valid

airtime_mvc/public/js/airtime/dashboard/versiontooltip.js

@@ -29,7 +29,6 @@ function setupVersionQtip(){
                     button: true
                 }
             },
-            show: 'click',  /* Show on click */
             hide: false,    /* Don't hide on mouseout */
             position: {
                 my: "top right",