Merge pull request #3 from ricardohsd/master

Allowing methods and Proc to be used as maks
Minor fix to test the right attribute
Change the validator to handle 'allow_blank' and 'allow_nil' as the others validators

In the other words by default allow_blank and allow_nil is false
Refactor the validator specs with a new RSpec matcher
Release a new version 0.2.1
Update the README file to recommend the new version
Improve the README file
Use ruby syntax for some code in README file
Fix and refactoring mask_validator

Now mask_validator can be used with no active
record models

- Added normalize_value method to check if the
  object respond to <attribute>_before_type_cast,
  implemented only in active record objects
Merge pull request #4 from norbaoliveira/master

Fix and refactoring mask_validator adding support to no active record classes
Add gem badge to show the last version

See more: http://badge.fury.io/
Set default message to 'invalid'

The default message should be 'invalid'.