Improve dev tooling (#30)

* added ex_check and got it passing

* Set up ex_check to run in test env

* Added static code analysis

* Updated actions file

* Updated dockerfile

docker-compose.ci.yml

@@ -4,6 +4,8 @@ services:
     build:
       context: .
       dockerfile: dev.Dockerfile
+    environment:
+      - MIX_ENV=test
     volumes:
       - '.:/app'
     ports: