Add gin-redis-ip-limiter middleware (#159)

* Add gin-redis-ip-limiter middleware

Add gin-redis-ip-limiter middleware in readme list.

* Update README.md

* Add description

README.md

@@ -36,4 +36,5 @@ Each author is responsible of maintaining his own code, although if you submit a
 + [xss-mw](https://github.com/dvwright/xss-mw) - XssMw is a middleware designed to "auto remove XSS" from user submitted input
 + [gin-helmet](https://github.com/danielkov/gin-helmet) - Collection of simple security middleware.
 + [gin-jwt-session](https://github.com/ScottHuangZL/gin-jwt-session) - middleware to provide JWT/Session/Flashes, easy to use while also provide options for adjust if necessary. Provide sample too.
-+ [gin-template](https://github.com/foolin/gin-template) - Easy and simple to use html/template for gin framework. 
++ [gin-template](https://github.com/foolin/gin-template) - Easy and simple to use html/template for gin framework.
++ [gin-redis-ip-limiter](https://github.com/Salvatore-Giordano/gin-redis-ip-limiter) - Request limiter based on ip address. It works with redis and with a sliding-window mechanism.