reorganization of _examples and add some new examples such as iris+groupcache+mysql+docker

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/response-writer/write-gzip/main.go

@@ -0,0 +1,24 @@
+package main
+
+import "github.com/kataras/iris/v12"
+
+func main() {
+	app := iris.New()
+	// app.Use(iris.Gzip)
+	// func(ctx iris.Context) { ctx.Gzip(true/false)}
+	// OR:
+	app.Get("/", func(ctx iris.Context) {
+		ctx.WriteGzip([]byte("Hello World!"))
+		ctx.Header("X-Custom",
+			"Headers can be set here after WriteGzip as well, because the data are kept before sent to the client when using the context's GzipResponseWriter and ResponseRecorder.")
+	})
+
+	app.Get("/2", func(ctx iris.Context) {
+		// same as the `WriteGzip`.
+		// However GzipResponseWriter gives you more options, like
+		// reset data, disable and more, look its methods.
+		ctx.GzipResponseWriter().WriteString("Hello World!")
+	})
+
+	app.Listen(":8080")
+}