196 rails default validation options missing from errors

[Mth0158]

Closes #196

This PR includes 2 commits:

• ab567ad: This commit have a lot a files changed because I had to create a lot of boilerplate to test it properly, it only impacts a few production features =>
  • The error_handler.rb file becomes the Errorable concern and gets a few upgrade to adress Rails default validation options missing from errors #196
  • The attached validator now does not accept the :allow_nil and :allow_blank options since it does not make sense to have these options with this validator
• 5a85ba7: A short commit that defines our validator concerns at the gem level instead that the global level

[Mth0158]

@igorkasyanchuk I would like to merge the #217 PR before this one though :)