update en doc and version check (#6876)

README.md

-README_cn.md
+README_en.md
\ No newline at end of file

docs/tutorials/INSTALL.md

@@ -22,7 +22,7 @@ Dependency of PaddleDetection and PaddlePaddle:
 
 | PaddleDetection version | PaddlePaddle version  |    tips    |
 | :----------------: | :---------------: | :-------: |
-|    develop           |       >= 2.2.2   |     Dygraph mode is set as default    |
+|    develop           |       develop   |     Dygraph mode is set as default    |
 |    release/2.5       |       >= 2.2.2   |     Dygraph mode is set as default    |
 |    release/2.4       |       >= 2.2.2   |     Dygraph mode is set as default    |
 |    release/2.3       |       >= 2.2.0rc |     Dygraph mode is set as default    |

docs/tutorials/INSTALL_cn.md

@@ -18,7 +18,7 @@ PaddleDetection 依赖 PaddlePaddle 版本关系：
 
 |  PaddleDetection版本  | PaddlePaddle版本  |    备注    |
 | :------------------: | :---------------: | :-------: |
-|    develop           |       >= 2.2.2    |     默认使用动态图模式    |
+|    develop           |       develop    |     默认使用动态图模式    |
 |    release/2.5       |       >= 2.2.2    |     默认使用动态图模式    |
 |    release/2.4       |       >= 2.2.2    |     默认使用动态图模式    |
 |    release/2.3       |       >= 2.2.0rc  |     默认使用动态图模式    |

ppdet/utils/check.py

@@ -87,7 +87,7 @@ def check_gpu(use_gpu):
         pass
 
 
-def check_version(version='2.0'):
+def check_version(version='2.2'):
     """
     Log error and exit when the installed version of paddlepaddle is
     not satisfied.
@@ -100,8 +100,19 @@ def check_version(version='2.0'):
         paddle_version.major, paddle_version.minor, paddle_version.patch,
         paddle_version.rc
     ]
+
+    # Paddledet develop version is only used on Paddle develop 
+    if version_installed == ['0', '0', '0', '0'] and version != 'develop':
+        raise Exception(
+            "PaddlePaddle version {} or higher is required, and develop version is only used for PaddleDetection develop version!".
+            format(version))
+
     if version_installed == ['0', '0', '0', '0']:
         return
+
+    if version == 'develop':
+        raise Exception("PaddlePaddle develop version is required!")
+
     version_split = version.split('.')
 
     length = min(len(version_installed), len(version_split))