add quick_start_en.md

docs/source/md/quick_start_en.md

+# Quick Start
+## How to install PLSC
+
+PLSC requires python 2.7 or above versions.
+
+First, you have to install PaddlePaddle. Using the following command to install paddlepaddle:
+```shell script
+pip install paddlepaddle-gpu>=1.6.2
+```
+For now, paddlepaddle-gpu is required.
+
+Then, install PLSC using pip:
+
+```shell script
+pip install plsc
+```
+
+## How to do train and validation
+The following example code shows how to train a model with PLSC.
+```python
+from plsc import Entry
+
+if __name__ == "__main__":
+    ins = Entry()
+    ins.set_train_epochs(1)
+    ins.set_model_save_dir("./saved_model")
+    # ins.set_with_test(False)  # 当没有验证集时，请取消该行的注释
+    # ins.set_loss_type('arcface')  # 当仅有一张GPU卡时，请取消该行的注释
+    ins.train()
+```
+
+And use the following command to start the train.
+```shell script
+python -m paddle.distributed.launch \
+    --cluster_node_ips="127.0.0.1" \
+    --node_ip="127.0.0.1" \
+    --selected_gpus=0,1,2,3,4,5,6,7 \
+    train.py
+```
+
+The following example code shows how to do model validation with PLSC.
+```python
+from plsc import Entry
+
+if __name__ == "__main__":
+    ins = Entry()
+    ins.set_checkpoint_dir("./saved_model/0/")
+    ins.test()
+```