add sample environment files

Author: ganezasan

Diff for: .env.app.testing

@@ -0,0 +1,4 @@
+POSTGRES_HOST=db
+PGUSER=postgres
+PGPASSWORD=postgres
+RAILS_ENV=development

Diff for: .env.db.testing

@@ -0,0 +1,3 @@
+POSTGRES_USER=postgres
+POSTGRES_PASSWORD=postgres
+POSTGRES_DB=rails_blog_dev