Restore Ruby 1.8.7 compatibility with lambda styles etc.

You'll hate me for this, I know, but 0.2.3 broke 1.8 compatibility in lib/.  spec/ had a couple of issues already but otherwise 0.2.2 worked great, despite 87b2158.
Nothing AFAICT, as https://github.com/domcleal/apipie-rails/blob/ruby18/lib/apipie/validator.rb#L24 calls this with the options argument every time.