Add README.

Author: hsluoyz

README.md

@@ -1 +1,66 @@
-# django-casbin
+# django-casbin 
+
+[![Join the chat at https://gitter.im/gin-gonic/gin](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/gin-gonic/gin)
+
+django-casbin is an authorization middleware for [Django](https://www.djangoproject.com/), it's based on [PyCasbin](https://github.com/casbin/pycasbin).
+
+## Installation
+
+```
+pip install django-casbin
+```
+
+## Simple Example
+
+- Add the middleware to your Django app's ``settings.py``:
+
+```python
+MIDDLEWARE = [
+    'django.middleware.security.SecurityMiddleware',
+    'django.contrib.sessions.middleware.SessionMiddleware',
+    'django.middleware.common.CommonMiddleware',
+    'django.middleware.csrf.CsrfViewMiddleware',
+    'django.contrib.auth.middleware.AuthenticationMiddleware',
+    'django.contrib.messages.middleware.MessageMiddleware',
+    'django.middleware.clickjacking.XFrameOptionsMiddleware',
+    'casbin_middleware.middleware.CasbinMiddleware', # Add this line, must after AuthenticationMiddleware.
+]
+```
+
+- In ``casbin_middleware/middleware.py``:
+
+```python
+import casbin
+
+    def __init__(self, get_response):
+        self.get_response = get_response
+        # load the casbin model and policy from files, database is also supported.
+        self.enforcer = casbin.Enforcer("casbin_middleware/authz_model.conf", "casbin_middleware/authz_policy.csv")
+
+    def check_permission(self, request):
+        # check the permission.
+        user = request.user.username
+        if request.user.is_anonymous:
+            user = 'anonymous'
+        path = request.path
+        method = request.method
+        return self.enforcer.enforce(user, path, method)
+```
+
+## Documentation
+
+The authorization determines a request based on ``{subject, object, action}``, which means what ``subject`` can perform what ``action`` on what ``object``. In this plugin, the meanings are:
+
+1. ``subject``: the logged-in user name
+2. ``object``: the URL path for the web resource like "dataset1/item1"
+3. ``action``: HTTP method like GET, POST, PUT, DELETE, or the high-level actions you defined like "read-file", "write-blog"
+
+For how to write authorization policy and other details, please refer to [the Casbin's documentation](https://casbin.org).
+
+## Getting Help
+
+- [Casbin](https://casbin.org)
+
+## License
+
+This project is under Apache 2.0 License. See the [LICENSE](LICENSE) file for the full license text.