Use parallel Coveralls reports in GitHub Actions (#213)

* cache pip dependencies and run parallel coveralls builds.

.github/workflows/browser-tests.yaml

@@ -6,7 +6,7 @@ name: browser
 on: [push, pull_request]
 
 jobs:
-  build:
+  tests:
 
     runs-on: ubuntu-latest
 
@@ -22,15 +22,39 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
 
+    - name: Cache pip
+      uses: actions/cache@v2
+      with:
+        # This path is specific to Ubuntu
+        path: ~/.cache/pip
+        # Look to see if there is a cache hit for the corresponding requirements file
+        key: ${{ runner.os }}-pip-${{ hashFiles('requirements.txt') }}
+        restore-keys: |
+          ${{ runner.os }}-pip-
+          ${{ runner.os }}-
+
     - name: Install Dependencies
       run: |
         python -m pip install --upgrade pip
         pip install -r browser/requirements.txt
         pip install -r browser/requirements-test.txt
 
-    - name: Test
+    - name: Run PyTest and Coveralls
       env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        COVERALLS_REPO_TOKEN: ${{ secrets.COVERALLS_REPO_TOKEN }}
+        COVERALLS_FLAG_NAME: ${{ matrix.python-version }}
+        COVERALLS_PARALLEL: true
       run: |
         pytest browser --cov browser --pep8
         coveralls
+
+  coveralls:
+    name: Finish Coveralls
+    needs: tests
+    runs-on: ubuntu-latest
+    steps:
+    - name: Coveralls Finished
+      uses: coverallsapp/github-action@master
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
+        parallel-finished: true