Android Updates in new build environment (August 2014)

Summary:
- build-tools-20.0.0 is now preinstalled
- thanks to great help of https://github.com/travis-ci/travis-build/pull/285, I don't think it is necessary adapt the documentation.

@BanzaiMan this is an "overkill" example, to illustrate the usage of this "upcoming updates" branch (201408-vm-update).