Sponsor & Partner attributes renamed to start_date; in both models set_defaults now runs after_initialize; changes made in validator and specs
Create new custom attribute validator DateNotInFuture with spec; replace previous validator in Partner & Sponsor models
Code review: move validator to lib/validators; move test class definition to spec file
Rebase after PR16 merge & add (not)valid expectation to validator spec
Made Sampriti happy :)
Merge pull request #17 from NikitaAvvakumov/improve_date_validator

Refactoring Date Validator.