Multiple version of PHP for testing (#33)

* Attempt multiple version of PHP for testing

* Update config.yml

* Use combination of workflows

.circleci/config.yml

@@ -1,7 +1,16 @@
 version: 2
 
 jobs:
-  build:
+  build_7.3:
+    docker: 
+      - image: circleci/php:7.3
+    working_directory: ~/ReadOnlyTraitLaravel
+    steps: # a set of executable commands
+      - checkout
+      - run: sudo composer self-update
+      - run: composer install -n --prefer-dist
+      - run: ./vendor/bin/kahlan -reporter=verbose
+  build_latest:
     docker: 
       - image: circleci/php:latest
     working_directory: ~/ReadOnlyTraitLaravel
@@ -10,3 +19,9 @@ jobs:
       - run: sudo composer self-update
       - run: composer install -n --prefer-dist
       - run: ./vendor/bin/kahlan -reporter=verbose
+workflows:
+  version: 2
+  build:
+    jobs:
+      - build_7.3
+      - build_latest