credit card validation refactoring using credit_card_validations

[Fivell]

this solves #52

• removed obsolete brands
• credit_card_validations supported brands
• added ability to validate by multiple brands, eg type: [:amex, :visa]
• fixes luhn validation checks (not all credit card brands use lunh validation)
• more strict validation (valid lunh is not enough to detect brand)

[franckverrot]

Great! Thanks! I'll release a new version ASAP.

Thanks again!