make the positioning of Go flags clearer in the help text

We did say "garble flags before the command" towards the end,
but let's also make that clearer at the top.

For #342.

main.go

@@ -54,7 +54,7 @@ var (
 func init() {
 	flagSet.Usage = usage
 	flagSet.BoolVar(&flagGarbleLiterals, "literals", false, "Obfuscate literals such as strings")
-	flagSet.BoolVar(&flagGarbleTiny, "tiny", false, "Optimize for binary size, losing the ability to reverse the process")
+	flagSet.BoolVar(&flagGarbleTiny, "tiny", false, "Optimize for binary size, losing some ability to reverse the process")
 	flagSet.StringVar(&flagDebugDir, "debugdir", "", "Write the obfuscated source to a directory, e.g. -debugdir=out")
 	flagSet.StringVar(&flagSeed, "seed", "", "Provide a base64-encoded seed, e.g. -seed=o9WDTZ4CN4w\nFor a random seed, provide -seed=random")
 }
@@ -63,7 +63,7 @@ func usage() {
 	fmt.Fprintf(os.Stderr, `
 Garble obfuscates Go code by wrapping the Go toolchain.
 
-	garble [garble flags] command [arguments]
+	garble [garble flags] command [go flags] [go arguments]
 
 For example, to build an obfuscated program: