Add a new .lazy modifier to mimic behavior of v1

Author: simplesmiler

index.js

@@ -14,6 +14,12 @@ export var focus = {
   },
 
   componentUpdated: function(el, binding) {
+    if (binding.modifiers.lazy) {
+      if (Boolean(binding.value) === Boolean(binding.oldValue)) {
+        return;
+      }
+    }
+
     if (binding.value) el.focus();
     else el.blur();
   },