docs(readme): update outdated install info

weakish · weakish · commit 56e9ce42a4c7 · 2019-06-19T17:56:54.000+08:00
The package name has changed from leancloud-sdk
to leancloud long long ago.
diff --git a/README.md b/README.md
@@ -7,13 +7,13 @@ LeanCloud Python SDK
 ## Install
 
 ```bash
-pip install leancloud-sdk
+pip install leancloud
 ```
 
 or
 
 ```
-easy_install leancloud-sdk
+easy_install leancloud
 ```
 
 Maybe you need the `sudo` prefix depends on your OS environment.
