Update GitHub Actions workflow to use latest GoogleCloudPlatform located actions (#171)

The locations of the Actions were moved around for some reason, resulting in 404s.

.github/workflows/main.yml

@@ -8,17 +8,16 @@ jobs:
     name: Google Cloud Build
     runs-on: ubuntu-latest
     steps:
+
     - uses: actions/checkout@master
-    # - run:
-    - name: Authenticate w/ Google Cloud
-      uses: actions/gcloud/auth@master
-      env:
-        GCLOUD_AUTH: ${{ secrets.GCLOUD_AUTH }}
-    - name: Build, Test, Push to GCR
-      uses: actions/gcloud/cli@master
+
+    - uses: GoogleCloudPlatform/github-actions/setup-gcloud@master
       with:
-        entrypoint: bash
-        args: |
-          -l -c "BRANCH_NAME=$GITHUB_REPOSITORY/$(expr $GITHUB_REF : '.*/\(.*\)') && \
-          BRANCH_NAME=${BRANCH_NAME,,} && \
-          gcloud builds submit . --config cloudbuild.yaml --project zealous-zebra --substitutions BRANCH_NAME=$BRANCH_NAME"
+        version: '275.0.0'
+        service_account_key: ${{ secrets.GCLOUD_AUTH }}
+
+    - name: Build, Test, Push to GCR
+      run: |
+        BRANCH_NAME=$GITHUB_REPOSITORY/$(expr $GITHUB_REF : '.*/\(.*\)') && \
+        BRANCH_NAME=${BRANCH_NAME,,} && \
+        gcloud builds submit . --config cloudbuild.yaml --project zealous-zebra --substitutions BRANCH_NAME=$BRANCH_NAME