Create connection with MongoDB

We should make connection with MongoDB With some certain ```Auth key``` file not upload. 
Connect detail:
1. A function can connect DB
2. A function can check is connect to DB
3. A function to close connection 
4. What if lost connection? need to deal with this

Auth Key Detail: 
1. url
2. port 
3. user
4. password
5. options

Should prove Unit Test as well.
