Merge pull request #73 from killme2008/master

Fixed AV.File doc

Author: wangxiao

lib/file.js

@@ -303,6 +303,8 @@
    *     // The file either could not be read, or could not be saved to AV.
    *   });
    * }</pre>
+   *
+   * @class
    * @param type {String} Optional Content-Type header to use for the file. If
    *     this is omitted, the content type will be inferred from the name's
    *     extension.