NINO validation (UK).
jruby-head is no longer supported

Travis-CI's jobs crashes when building with jruby-head.

Let's work without it until the next major release, and decide wether or not we should keep it in the future.
Starting today, only JRuby for Ruby 1.9 is supported on the master branch.
Merge pull request #60 from Loremaster/nino

NINO validation (UK).
Grammar fixes
Reintroduce jruby-head

Also, this commit allows the build to fail only for jruby-head
Add Barcode Validator + tests
Add comments and update tests
Update doc for BarcodeValidator
Merge pull request #61 from pbechu/barcode-validator

Barcode validator
Mention the new barcode validator
Add Pierre-Baptiste to the contrib list
Replace unary + operator in favor of its binary version

Here's a nice explanation for future reference:
https://stackoverflow.com/questions/16624131/what-do-def-and-def-mean
Remove extra chars from the require's
Introduce ActiveValidators.activate for 3.0.0
Release 3.0.0
Release 3.0.1

This release stops require all the validators by default
Handle errors with validation format of barcodes
Add some doc to BarcodeValidator
Update list of format supported
Merge pull request #63 from pbechu/barcode-validator

check_validity! for BarcodeValidator