Update Mocha to 8.1 (#57)

This change updates mocha to 8.1. This should take care of the minimist
security warning.

Author: lhchavez

.github/workflows/ci.yml

@@ -17,10 +17,10 @@ jobs:
         uses: actions/checkout@v2
 
       - name: Install JavaScript dependencies
-        run: yarn install
+        run: npm ci
 
       - name: Run JavaScript tests
-        run: yarn test
+        run: npm test
 
   python-test:
     name: Python Tests