Feature #4977: Refactor API of AssetsManager
Feature #4977: Add UPDATE_FAILED event
Feature #4977: Add UPDATE_FAILED event in test case
Feature #4977: Refactor Downloader::prepareDownload
Feature #4977: Refactor Downloader::batchDownload with curl_multi_perform
Feature #4977: Make downloadProgressFunc friend of AssetsManager
Feature #4977: Use a new thread for batch download
Feature #4977: Improve batchDownload logic and walkthrough the new curl multi perform process
Feature #4977: Improve error handling with curl error code returned
Feature #4977: Add batchDownload finish notification
Feature #4977: Improve and secure error handling
Feature #4977: Add AssetsManager::getFailedAssets and updateAssets function
Feature #4977: Add path information to removeDirectory error message
Feature #4977: Improve updateAssets function
Merge branch 'lua-vm' of https://github.com/dumganhar/cocos2d-x into lua-vm
Feature #4977: Remove CURL dependency in headers
Feature #4977: Improve AssetsManager updateAssets process and support continue progression
Feature #4977: Fix lua compilation issues
Merge pull request #48 from pandamicro/lua-vm

Using curl_multi_perform in batchDownload, Add getFailedAssets, updateAssets function and improve error handling