Add script to run headless tests easily
Add script to run headless tests easily

Summary:
It's not obvious how to run the headless tests at the moment, and requires manual steps this adds a script to do it.
It still does not start an emulator or the sample app, but it's an improvement.

Reviewed By: passy

Differential Revision: D17155308

fbshipit-source-id: 846b87389823f422030470807aa4aabacce69179

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