Error:Access to the dex task is now impossible, starting with 1.4.0
1.4.0 introduces a new Transform API allowing manipulation of the .class files.
See more information: http://tools.android.com/tech-docs/new-build-system/transform-api

解决办法：

修改为：

classpath 'com.android.tools.build:gradle:1.3.0'

连接：

http://stackoverflow.com/questions/32579192/access-to-the-dex-is-now-impossible-starting-with-1-4-0