Provide test build

[PerfectSlayer]

A CI (continuous integration) has been deployed on Travis.
The goal is to provide the latest test builds automatically.
Actually, debug builds are hosted on Google Cloud Storage.

To finish the CI installation, I need to:

• Create / get the cryptographic keys to sign the app,
• Securely deploy the keys on the CI (travis encrypt?),
• Update deploy script to sign the app,
• Update deploy script to upload/publish the app.