Migrate PyPI release to GitHub Actions

[seisman]

Description of proposed changes

This PR migrate the PyPI release job from Travis CI to GitHub Actions.

References:

• https://packaging.python.org/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows.
• https://github.com/fatiando/boule/tree/master/.github/workflows

Address #566

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If adding new functionality, add an example to docstrings or tutorials.

Notes

• You can write /format in the first line of a comment to lint the code automatically

[weiji14]

I made a suggestion following @leouieda's PR at fatiando/pooch#196. However, I'm not sure if I like this workaround, since we will have to switch from versioneer to setuptools_scm (#671) sooner or later.

[seisman]

See the "fake" release in the test pypi repository: https://test.pypi.org/project/pygmt/0.2.0.post0.dev52/#history

[leouieda]

I would actually recommend looking at the workflows here instead: https://github.com/fatiando/boule/tree/master/.github/workflows We're also trying out a tool called nox. It's pretty nice to automate some tasks with Python instead of clunky Makefiles that don't work on Windows.

[weiji14]

These changes will have to be documented under MAINTENANCE.md. Could you remove mention of Travis CI PyPI deployments at https://github.com/GenericMappingTools/pygmt/blob/v0.2.0/MAINTENANCE.md#travis-ci and place it under the Github Actions section at https://github.com/GenericMappingTools/pygmt/blob/v0.2.0/MAINTENANCE.md#github-actions instead please?

[weiji14]

Getting there! Just one minor suggestion to change 'archive' to 'wheel'.

[weiji14]

Cool, thanks for doing this @seisman, and to @leouieda for your experience on the fatiando side! This will really streamline our CI going forward 😄

P.S. remember to disable the Pull Request trigger.