Merge pull request #23 from yaplas/refactor/validations

change address and phone number validations
fix validate when value undefined
Merge pull request #24 from benjamine/master

fix validate when value undefined
0.1.6
required field validation
Merge pull request #25 from benjamine/master

required field validation
0.1.7
empty value is never invalid
Merge pull request #26 from benjamine/master

empty value is never invalid
0.1.8
Remove some states.
Ask julia in #864
Merge pull request #27 from jonymusky/fix/remove-states

Remove some states.
0.1.9
refactor: use json schema to validate models
delete unused code