insert the header file to match python3 style print()

01.fit_a_line/README.cn.md

@@ -100,6 +100,7 @@ $$MSE=\frac{1}{n}\sum_{i=1}^{n}{(\hat{Y_i}-Y_i)}^2$$
 import paddle
 import paddle.fluid as fluid
 import numpy
+from __future__ import print_function
 ```
 
 我们通过uci_housing模块引入了数据集合[UCI Housing Data Set](https://archive.ics.uci.edu/ml/datasets/Housing)

01.fit_a_line/README.md

@@ -108,6 +108,7 @@ Our program starts with importing necessary packages:
 import paddle
 import paddle.fluid as fluid
 import numpy
+from __future__ import print_function
 ```
 
 We encapsulated the [UCI Housing Data Set](https://archive.ics.uci.edu/ml/datasets/Housing) in our Python module `uci_housing`.  This module can

01.fit_a_line/index.cn.html

@@ -142,6 +142,7 @@ $$MSE=\frac{1}{n}\sum_{i=1}^{n}{(\hat{Y_i}-Y_i)}^2$$
 import paddle
 import paddle.fluid as fluid
 import numpy
+from __future__ import print_function
 ```
 
 我们通过uci_housing模块引入了数据集合[UCI Housing Data Set](https://archive.ics.uci.edu/ml/datasets/Housing)

01.fit_a_line/index.html

@@ -150,6 +150,7 @@ Our program starts with importing necessary packages:
 import paddle
 import paddle.fluid as fluid
 import numpy
+from __future__ import print_function
 ```
 
 We encapsulated the [UCI Housing Data Set](https://archive.ics.uci.edu/ml/datasets/Housing) in our Python module `uci_housing`.  This module can