Move DevOps stuff to a separate repo

[soygul]

• GitHub releases (travis.yml).
• Google Play Store releases (release.sh).
• et. al.

We need to keep this repo open-source related only. Having travis github deployment scripts doesn't help people who wants to deploy nbusy internally.

[soygul]

• github.com/nbusy/build
• inside a docker container:
  • pull and start nbusy/nbusy docker image
  • checkout nbusy/nbusy-android repo
  • build the Android app
  • run tests
  • publish to play store