Improve vfsgen to not unzip bindata files but send to browser directly (#7109)

* Don't unzip files from bindata but send to browser directly

* remove dependent for httpgzip

* Add tests for parseAcceptEncoding

* Update docs for ENABLE_GZIP

* Fix bug

* Fix bug

Co-authored-by: zeripath <art27@cantab.net>

modules/public/dynamic.go

@@ -6,9 +6,19 @@
 
 package public
 
-import "net/http"
+import (
+	"io"
+	"net/http"
+	"os"
+	"time"
+)
 
 // Static implements the macaron static handler for serving assets.
 func Static(opts *Options) func(next http.Handler) http.Handler {
 	return opts.staticHandler(opts.Directory)
 }
+
+// ServeContent serve http content
+func ServeContent(w http.ResponseWriter, req *http.Request, fi os.FileInfo, modtime time.Time, content io.ReadSeeker) {
+	http.ServeContent(w, req, fi.Name(), modtime, content)
+}