(#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/view/template_html_1/main.go

@@ -16,7 +16,7 @@ func main() {
 	// TIP: append .Reload(true) to reload the templates on each request.
 
 	app.Get("/", func(ctx iris.Context) {
-		ctx.Gzip(true)
+		ctx.Compress(true)
 		ctx.ViewData("", mypage{"My Page title", "Hello world!"})
 		ctx.View("mypage.html")
 		// Note that: you can pass "layout" : "otherLayout.html" to bypass the config's Layout property