Update 3.insertionSort.md

LokiSharp · web-flow · commit 1eb34183ad87 · 2017-01-21T21:16:15.000+08:00
diff --git a/3.insertionSort.md b/3.insertionSort.md
@@ -36,7 +36,7 @@ function insertionSort(arr) {
 }
 ```
 
-## 3. Python 代码实现
+## 4. Python 代码实现
 
 ```python
 def insertionSort(arr):
