fix javascript for signup modal .click() in index.html for safari

lms/templates/index.html

@@ -148,7 +148,26 @@
 % if show_signup_immediately is not UNDEFINED:
 <script type="text/javascript">
 function dosignup(){
-    document.getElementById('signup').click();
+    comp = document.getElementById('signup');
+try { //in firefox
+    comp.click();
+    return;
+} catch(ex) {}
+try { // in old chrome
+    if(document.createEvent) {
+        var e = document.createEvent('MouseEvents');
+        e.initEvent( 'click', true, true );
+        comp.dispatchEvent(e);
+        return;
+    }
+} catch(ex) {}
+try { // in IE, safari
+    if(document.createEventObject) {
+         var evObj = document.createEventObject();
+         comp.fireEvent("onclick", evObj);
+         return;
+    }
+} catch(ex) {}
 }
 $(window).load(dosignup);
 </script>