Add gin-health-check middleware (#171)

README.md

@@ -41,3 +41,4 @@ Each author is responsible of maintaining his own code, although if you submit a
 + [gin-method-override](https://github.com/bu/gin-method-override) - Method override by POST form param `_method`, inspired by Ruby's same name rack
 + [gin-access-limit](https://github.com/bu/gin-access-limit) - An access-control middleware by specifying allowed source CIDR notations.
 + [gin-stats](https://github.com/semihalev/gin-stats) - Lightweight and useful request metrics middleware
++ [gin-health-check](https://github.com/RaMin0/gin-health-check) - A health check middleware for Gin