Implement commands

Commands implemented

   $ minio put <objectname> <file>
   $ minio encode <objectname>
   $ minio get <objectname>
   $ minio list

TODO :

   $ minio init
   $ minio verify
    ...
    ...

pkgs/storage/appendstorage/append_storage.go

@@ -80,7 +80,7 @@ func NewStorage(rootDir string, slice int) (storage.ObjectStorage, error) {
 func (storage *appendStorage) Get(objectPath string) (io.Reader, error) {
 	header, ok := storage.objects[objectPath]
 	if ok == false {
-		return nil, nil
+		return nil, errors.New("Object not found")
 	}
 
 	offset := header.Offset