Upgrade to Chaos 0.4.8

Everything still works, and this adds the capability to work with a
different asset directory. This will use assets from the local
`src/main/resources/assets/app` directory:

    ./bin/start-chronos.bash --master zk://localhost:2181/mesos --zk_hosts localhost:2181 --assets_path src/main/resources/assets/app
Merge branch 'master' of https://github.com/airbnb/chronos
Merge pull request #156 from mesosphere/master

This fixes the installers