anchor.diff:  library task;
   
   import 'dart:convert';
  +import 'package:ddays/taskcategory.dart' show TaskCategory;
   
   class TaskNote {
     String notebody;
  
positive.code:     tasknotes.add(note);
    }
    
    void addCategory(String cat ) {
      taskcategories.add(cat);
    }
    void removeCategory(String cat) {
      taskcategories.remove(cat);
    }
  }
  
negative.code:   List<TaskNote> tasknotes = [];
    DateTime scheduled;
    int timestamp;
    Set<TaskCategory> taskcategories = new Set();
    Task(this.summary, [this.scheduled=null]) {
      this.timestamp = new DateTime.now().millisecondsSinceEpoch;
    }
  