Create source distribution release on PyPI

This documentation are not for the end-users. Only for core devs / maintainers.

Currently this is only for Plyer, PyJNIus and PyOBJus.

1. Bump version (or remove .dev0).

2. Create new stable branch, move old stable one to e.g. stable-X.Y.Z or X.Y.Z.

3. Set <PROJECT>_DEPLOY environment variable to 1 in Travis project settings, where <PROJECT> is one of the repo names e.g.: PLYER_DEPLOY=1

   Note: I tried to use it within Trigger build environment with name=value, but nothing happened, sooo... need to investigate more. (kwu)

4. Trigger a manual build on Travis.

5. Check PyPI according to the TWINE_REPOSITORY_URL in Travis settings.

6. Remove <PROJECT>_DEPLOY variable from the settings (or set to 0, but make it visible!)

7. Install package from PyPI and run tests if applicable and if they are present in the package.

8. Bump version in master branch and append .dev0 at the end of the version.