fix drop test issue

index.html

@@ -40,7 +40,7 @@
 
     <div id="kityminder" onselectstart="return false"></div>
 
-    <div id="share-dialog" >
+    <div id="share-dialog">
         <h3>URL分享：</h3>
         <p>
             <input id="share-url" type="url" value="http://naotu.baidu.com/?shareId=kcev3dd" />

src/module/dragtree.js

@@ -300,7 +300,12 @@ var TreeDragger = kity.createClass('TreeDragger', {
             function area(box) {
                 return box.width * box.height;
             }
-            return intersectBox && area(intersectBox) > 0.5 * Math.min(area(sourceBox), area(targetBox), 1e4);
+            if (!intersectBox) return false;
+            // 面积判断
+            if (area(intersectBox) > 0.5 * Math.min(area(sourceBox), area(targetBox))) return true;
+            if (intersectBox.width + 1 >= Math.min(sourceBox.width, targetBox.width)) return true;
+            if (intersectBox.height + 1 >= Math.min(sourceBox.height, targetBox.height)) return true;
+            return false;
         });
         this._renderDropHint(this._dropSucceedTarget);
         return !!this._dropSucceedTarget;