feat(ci): run CI/tests on GitHub Actions (#215)

Use GitHub Actions to run automated tests whenever a pull request targets `master`, or a commit is merged to `master`.

Alternative if our current and previous CI systems: CircleCI and TravisCI.

This reference helped a lot: [Workflow syntax for GitHub Actions - GitHub Help](https://help.github.com/en/articles/workflow-syntax-for-github-actions)

Related: #205.

.github/workflows/nodejs.yml

@@ -10,13 +10,16 @@ on:
 
 jobs:
   build:
-
     runs-on: ubuntu-latest
-
+    services:
+      mongodb:
+        image: docker://mongo:3.4
+        ports:
+        - 27017:27017
     strategy:
       matrix:
         node-version: [8.x]
-
+    # needs: mongodb
     steps:
     - uses: actions/checkout@v1
     - name: Use Node.js ${{ matrix.node-version }}