enable a more extensive build matrix on travis
enable a more extensive build matrix on travis

- js builds only need js tooling, so we use travis' docker-based
  containers for fast boot. this trims the runtime for js-tests from
  around 3-4 minutes to about 45-50 seconds.

- android builds have a dedicated `android` environment that we can take
  advantage of. use it. this drops the time from ~20 minutes to ~9.

- i added the tooling to support running an android emulator on the new
  builds. however, it takes about 20 minutes to run the android tests on
  this system because of the emulator. when we decide to build more
  tests for the emulator, this will be useful.

- os x / ios builds still use the same image.

carls-app/carls,StoDevX/AAO-React-Native,StoDevX/AAO-React-Native,carls-app/carls,carls-app/carls,StoDevX/AAO-React-Native,carls-app/carls,StoDevX/AAO-React-Native,StoDevX/AAO-React-Native,carls-app/carls,carls-app/carls,carls-app/carls,StoDevX/AAO-React-Native,StoDevX/AAO-React-Native,StoDevX/AAO-React-Native,StoDevX/AAO-React-Native