Merge pull request #7 from dobestan/develop

[Sprint #2] init teams app and update user model
add invalid code into validation error
change test_phonenumber.py
add password field into REQUIRED_FIELDS
add, change invalid phone number variable
add regex validation method for phone number
add regex digit validation for phone number
add get_user method for user models
add test code for Retrieve user(get_user)
add test code for delete_user
complete get_user method
update test code for delete_user
complete test code for delete_user
complete # 2 test code for delete_user
add delete_user method for UserManager
change contents delete_user method
update regular expression in validation method
add test_code, method for update_user phone number
add test code & contents of update_user method for name
add test code, validation code for user not test_name, models