support license for compress css

bruce/css/bootstrap.css

@@ -1,4 +1,4 @@
-/*!
+/**
  * Copyright (c) 2010-2016, b3log.org & hacpai.com
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/*! normalize.css v3.0.1 | MIT License | git.io/normalize */
+/** normalize.css v3.0.1 | MIT License | git.io/normalize */
 html {
   font-family: sans-serif;
   -webkit-text-size-adjust: 100%;