Roll Observatory packages and add a roll script

packages/charted/lib/charts/chart_data.dart

 //
 // Copyright 2014 Google Inc. All rights reserved.
 //
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 //
 
 part of charted.charts;
 
@@ skipping 101 matching lines @@
     return null;
   }
 
   ChartColumnSpec({this.label, String type : TYPE_NUMBER,
       this.formatter, bool useOrdinalScale})
       : useOrdinalScale =
             useOrdinalScale == true ||
             useOrdinalScale == null && ORDINAL_SCALES.contains(type),
         type = type;
 }