Migrate continuous integration to GitHub Actions

[agitter]

The initial goal is to replicate the AppVeyor test. If possible, I will add headless testing of the ml4bio command.

This will replace the AppVeyor Windows test and Travis CI Linux test.

[agitter]

I updated the AppVeyor project settings to select "Skip branches without appveyor.yml" and deleted that config file. That disabled AppVeyor.

Removing .travis.yml disabled the Travis CI builds for subsequent commits.

I removed the xvfb test of the ml4bio command. Even if the command does not exist, the test still passes. A plugin such as https://github.com/pytest-dev/pytest-qt would be better for testing the GUI.

I also added start up message "Starting ml4bio version 0.1.3".

[agitter]

This doesn't change the ml4bio package so I'm going to merge.