Upgrade to official build tools 1.0 and add gradle wrapper.

The wrapper is for people who might be on Windows or not used to a gradle build system. They can just run commands with ./gradlew instead of having to install gradle themselves.

Sorry for so many PR's so quickly! Not sure if you wanted them in bigger pieces or smaller ones :\
Hm this is still showing 5 in my diff - is this line updated?

<uses-sdk android:minSdkVersion="4" />