3.0.0alpha8

androidstudio的gradle更新到3.0.0-beta2版本后，出现Gradle'xxxx'projectrefreshfailed错误，和Gredleprojectsyncfailed.Basicfunctionality(e.g.editing,debugging)willnotworkproperly，用3.0.0-alpha8替换掉3.0.0-beta2。