move bencode to subdirectory

making room for other packages

bencode/README.md

@@ -0,0 +1 @@
+this is a copy from code.google.com/p/bencode-go

bencode/struct.go

@@ -534,5 +534,7 @@ func isValueNil(val reflect.Value) bool {
 // an infinite recursion.
 //
 func Marshal(w io.Writer, val interface{}) error {
+  // TODO match other encoders, like encoding/json ...
+  // func Marshal(v interface{}) ([]byte, error)
 	return writeValue(w, reflect.ValueOf(val))
 }