Add comments to server.js and main.js

[schneedotdev]

Add comments to server.js and main.js in order to detail code functionality and allow for easy code maintenance.

in main.js

• include authors of files
• include description of app
• include documentation for each function

in server.js

• include information about each endpoint
• detail MongoDB usage
• describe database manipulation

[schneedotdev]

I would like to assign myself to this issue. I have submitted a PR addressing this issue: #42