Add PureJSON renderer (#694)

Closes #693

README.md

@@ -991,6 +991,34 @@ func main() {
 }
 ```
 
+#### PureJSON
+
+Normally, JSON replaces special HTML characters with their unicode entities, e.g. `<` becomes  `\u003c`. If you want to encode such characters literally, you can use PureJSON instead.
+This feature is unavailable in Go 1.6 and lower.
+
+```go
+func main() {
+	r := gin.Default()
+	
+	// Serves unicode entities
+	r.GET("/json", func(c *gin.Context) {
+		c.JSON(200, gin.H{
+			"html": "<b>Hello, world!</b>",
+		})
+	})
+	
+	// Serves literal characters
+	r.GET("/purejson", func(c *gin.Context) {
+		c.PureJSON(200, gin.H{
+			"html": "<b>Hello, world!</b>",
+		})
+	})
+	
+	// listen and serve on 0.0.0.0:8080
+	r.Run(":8080)
+}
+```
+
 ### Serving static files
 
 ```go