Merge pull request #4 from alno/rails4_compatible_gemspec

Loosen dependecies: gem is compatible with Rails4
README example fix
better credit card number sanitizing
version bump
support for brands: :any  syntax  for activemodel validator
Merge branch 'master' of https://github.com/Fivell/credit_card_validations
travis config
travis config only 1.9+
Allow brand restriction when detecting