release 2.8.4

Log : release 2.8.3

Log : release 2.8.2

Log:release 2.8.1

release: 2.8.0

1.add GetObjectAcl，DeleteMultiObjects，ListBuckets, ImagePersist function

Merge branch 'master' of https://github.com/aliyun/aliyun-oss-android…

…-sdk

Log : release 2.7.2

Merge branch 'master' of https://github.com/aliyun/aliyun-oss-android…

…-sdk

log : release 2.7.0

Log : more log info