Add code style settings and update git ignore
A sinatra example
Finished CRUD RESTful API for User
Move sinatra project to service folder
Move some utils classes into utils dir
Move readme back to root
Refine utils and make return more literal, and fix user id

Combine/move utils
Refined error and return methods in utils
Fix user set email as id
Remove unused code
Make controllers into classes and move utils to controller base
Add RESTful API Doc markdown
Reorganize all files and temp remove classes structure
Add User validation API
Remove password hiding for user
Reconstruct code, classes are back, and move helpers
Reconstruct code, move helpers back to controllers, and add more validation helpers
Add category model and controller
Remove user security in API Doc
Remove all View API in Doc
Fix category model
Embedded Address model into User model
Use request scope variables, and validation parameters become optional