Modify usage in README

README.md

@@ -20,16 +20,28 @@ $ pip install redis-ratelimit
 The library itself is framework agnostic, but let's assume you want to use it with [Flask](http://flask.pocoo.org/docs/0.12/):
 
 ```python
+from http import HTTPStatus # python 3.4 +
 from flask import Flask, jsonify
+from flask import make_response
 from redis_ratelimit import ratelimit
+from redis_ratelimit.exceptions import RateLimited
 
 app = Flask(__name__)
 
 @app.route('/')
-@ratelimit(rate='10/m', key='ccc')
 @ratelimit(rate='2/s', key='ccc')
 def index():
     return jsonify({'status': 'OK'})
+
+def over_limit(e):
+    code = HTTPStatus.TOO_MANY_REQUESTS # 429
+    body = jsonify({"message":str(e)})
+    return make_response(body, code.value)
+
+app.register_error_handler(RateLimited, over) # flask error handler
+
+if __name__ == '__main__':
+    app.run()
 ```
 
 This will allow a total of 10 requests in any given minute, but no faster than 2 requests a second.