Connection code clean up

[stevenzhang717]

• clean up your connection code, you don't need to return a function, just return the object, if you import your module somewhere else, those object could be reuse
• extracted database creation script
  -add creation script to connection.js, please test if it works with your migration process.

[stevenzhang717]

you might want to check if the my db code could work with your db migration code, when i ran the first time, it had some transaction issue.

[JasonShin]

It doesn't contain connection code clean up. And could you please remove sql file since it won't be used?