Heroku integration with foreman

Add foreman configuration for Heroku:
- To test production configuration execute NODE_ENV=production foreman
  start
- Database connection configuration now handles "use_env_variable" which
  should be defined as a environment variable such as "DATABASE_URL"
  with a proper database URI connection string, ie:
  postgres://user:password@db.example.com:5432/database
- Added package.json configuration to run migrations and db seed after
  `npm install`

Update frontend models to match sequelize definition.
Update views to work according to the changes above.
Handling isCompleted and parentId apropiately for PostgreSQL databases

config/database.json

@@ -8,10 +8,6 @@
     "storage": "db/test.sqlite"
   },
   "production": {
-      "username": "postgres",
-      "password": "",
-      "database": "hackflowy",
-      "host"    : "localhost",
-      "dialect" : "postgres"
+      "use_env_variable": "DATABASE_URL"
   }
 }