というエラー。
MavenCentralRepositoryでは、
「0.6.2」なのですがこれが原因と。
com.android.tools.build:gradle:0.6.+
の記述を
com.android.tools.build:gradle:0.6.1
に変えましょうと。
NOTE: The Android Gradle 0.6.2 plugin that was published on Maven Central appears to have incorrect dependencies, which leads to ClassNotFoundExceptions during the build. Hold off updating for now, or if you have already updated, you can work around this by editing your build.gradle file and instead of depending on "0.6.+", depend on "0.6.1".