Adds conditional rendering (#139)

Author: jcleigh

.gitignore

@@ -1,3 +1,4 @@
 .DS_Store
 *.log
 node_modules
+*.idea

src/SortableList.js

@@ -110,13 +110,21 @@ export default class SortableList extends Component {
           this._resolveRowLayout[key] = resolve;
         });
       });
-      this.setState({
-        animated: false,
-        data: nextData,
-        containerLayout: null,
-        rowsLayouts: null,
-        order: nextOrder
-      });
+
+      if (Object.keys(nextData).length > Object.keys(data).length) {
+        this.setState({
+          animated: false,
+          data: nextData,
+          containerLayout: null,
+          rowsLayouts: null,
+          order: nextOrder
+        });
+      } else {
+        this.setState({
+          data: nextData,
+          order: nextOrder
+        });
+      }
 
     } else if (order && nextOrder && !shallowEqual(order, nextOrder)) {
       this.setState({order: nextOrder});