ci: Convert .travis.yml to GitHub Actions

This converts most functionality, excluding Slack notifications, from
the Travis-CI.org configuration file into the GitHub Actions config.

Slack notifications will be taken up separately using the various
options available to us, and may result in a future pull request.

.github/workflows/make-test.yml

@@ -0,0 +1,17 @@
+name: make-test
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: docker/login-action@v1
+        with:
+          # GitHub.com > (this repo) > Settings > Secrets
+          username: ${{ secrets.DOCKER_HUB_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+      - name: Run make test
+        run: |
+          make test