## 2018-08-21 V2.1.0

    1. change default thread pool core size from 2 to 0
    2. support refresh when state is StateLoadCompleted
    3. bug fix: duplicate listener after listen data with same listener more than once

## 2018-01-23 V2.0.0
    
    1. add support for group pre-load task with GroupedDataLoader and GroupedDataListener

## 2018-01-05 V1.1.0 

    1. add javadoc for PreLoader 
    2. don`t accept listeners after pre-laod task has been destroyed

## 2018-01-01 V1.0.0 


    add support for remove DataListener dynamically

## 2018-01-01 V0.1.0 first commit