X turn example/hello to return real non-small content

I need this to compare speed wrt github.com/jacobsa/fuse which does not
have ready loopback demo.

Out of the box github.com/jacobsa/fuse turned out to be ~ 1.6x slower
than github.com/hanwen/go-fuse.

with github.com/hanwen/go-fuse:

        .../github.com/hanwen/go-fuse/example/benchmark-read-throughput$ md5sum ~/mnt/tmp/file.txt
        f4cbd65f70761c9c5306d9301422af02  /home/kirr/mnt/tmp/file.txt

        .../github.com/hanwen/go-fuse/example/benchmark-read-throughput$ go run readbench.go -bs 128 -limit 30000 ~/mnt/tmp/file.txt
        block size 128 kb: 30000.4 MB in 9.704823906s: 3091.29 MBs/s

with github.com/jacobsa/fuse

        .../github.com/hanwen/go-fuse/example/benchmark-read-throughput$ md5sum ~/mnt/tmp/hello
        f4cbd65f70761c9c5306d9301422af02  /home/kirr/mnt/tmp/hello

        .../github.com/hanwen/go-fuse/example/benchmark-read-throughput$ go run readbench.go -bs 128 -limit 30000 ~/mnt/tmp/hello
        block size 128 kb: 30000.4 MB in 15.701199318s: 1910.71 MBs/s

See also https://github.com/hanwen/go-fuse/issues/192#issuecomment-338198877

example/hello/main.go

@@ -9,6 +9,7 @@ package main
 import (
 	"flag"
 	"log"
+	"io/ioutil"
 
 	"github.com/hanwen/go-fuse/fuse"
 	"github.com/hanwen/go-fuse/fuse/nodefs"
@@ -41,6 +42,17 @@ func (me *HelloFs) OpenDir(name string, context *fuse.Context) (c []fuse.DirEntr
 	return nil, fuse.ENOENT
 }
 
+
+var data []byte
+func init() {
+	var err error
+        data, err = ioutil.ReadFile("/boot/initrd.img-4.16.0-2-amd64")
+        if err != nil {
+                panic(err)
+        }
+}
+
+
 func (me *HelloFs) Open(name string, flags uint32, context *fuse.Context) (file nodefs.File, code fuse.Status) {
 	if name != "file.txt" {
 		return nil, fuse.ENOENT
@@ -48,7 +60,9 @@ func (me *HelloFs) Open(name string, flags uint32, context *fuse.Context) (file
 	if flags&fuse.O_ANYWRITE != 0 {
 		return nil, fuse.EPERM
 	}
-	return nodefs.NewDataFile([]byte(name)), fuse.OK
+
+	return nodefs.NewDataFile(data), fuse.OK
+	//return nodefs.NewDataFile([]byte(name)), fuse.OK
 }
 
 func main() {