add users app to settings.py
update .gitignore : add sqlite database
basic user model : with email and password
update user model : using custom Manager named UserManager
update user model : validate user model
update user model : password length should be at least 6
update user model : is_admin and is_org_admin
update user model : is_active
update user model : name
Merge branch 'feature/modeling-user' into develop

* feature/modeling-user:
  update user model : name
  update user model : is_active
  update user model : is_admin and is_org_admin
  update user model : password length should be at least 6
  update user model : validate user model
  update user model : using custom Manager named UserManager
  basic user model : with email and password
  update .gitignore : add sqlite database
Merge branch 'release/v0.1'

* release/v0.1:
  update user model : name
  update user model : is_active
  update user model : is_admin and is_org_admin
  update user model : password length should be at least 6
  update user model : validate user model
  update user model : using custom Manager named UserManager
  basic user model : with email and password
  update .gitignore : add sqlite database