Fix sharing options between models

[iNecas]

@@class_variables are one of the worst ideas ever in Ruby and
they should burn in hell. Please don't use it ever again in any
software, unless you intend to make others' life miserable :)

Explanation: compare

module A
  def hello
    @@hello
  end

  def set_hello
    @@hello = self.name
  end
end

class B
  extend A
end

class C
  extend A
end

B.set_hello
C.set_hello
puts B.hello
puts C.hello

with

module A1
  def hello
    @hello
  end

  def set_hello
    @hello = self.name
  end
end

class B1
  extend A1
end

class C1
  extend A1
end

B1.set_hello
C1.set_hello
puts B1.hello
puts C1.hello

[rubiety]

Yep, looks like this was introduced in contributing pull request #12 and I didn't catch it. Thanks for the fix.

[iNecas]

Thanks for quick merge: if a new release could follow, that would be appreciated :)

[rubiety]

Just cut a release for v0.5.1 - enjoy!

[iNecas]

@rubiety++

[iNecas]

Seems there is still some issue with STIs, that can lead to undefined method []' for nil:NilClass
/usr/local/rvm/gems/ruby-2.1.5@test_plugin_pull_request-1/gems/validates_lengths_from_database-0.5.1/lib/validates_lengths_from_database.rb:37:in validate_lengths_from_database', working on fixing it now

[iNecas]

The additional issue should be handled in #18