sharng docker-compose.yml to add two separate container specifications:

one for development (that mounts the host git root to
/opt/letsencrypt/src) and one for production (that doesn't).

docker-compose.yml

@@ -1,7 +1,13 @@
-letsencrypt:
+production:
+  build: .
+  ports:
+    - "443:443"
+
+# For development, mount git root to /opt/letsencrypt/src in order to
+# make the dev workflow more vagrant-like.
+development:
   build: .
   ports:
     - "443:443"
   volumes:
-    - /etc/letsencrypt:/etc/letsencrypt
-    - /var/lib/letsencrypt:/var/lib/letsencrypt
+    - .:/opt/letsencrypt/src