(#1554) Add support for all common compressions (write and read)

- Remove the context.Context interface and export the *context, the iris.Context now points to the pointer\nSupport compression and rate limiting in the FileServer\nBit of code organisation


Former-commit-id: ad1c61bf968059510c6be9e7f2cceec7da70ba17

_examples/webassembly/main.go

@@ -17,7 +17,7 @@ func main() {
 	app.HandleDir("/", "./client")
 
 	app.Get("/", func(ctx iris.Context) {
-		// ctx.Gzip(true)
+		// ctx.Compress(true)
 		ctx.ServeFile("./client/hello.html")
 	})