Fixes broken bin/console
Fixes broken bin/console

Running bundle exec bin/console fails when it loads the fixtures as
Minitest module isn't defined at the point when PDC::Minitest::FixtureExtensions
are injected into Minitest::Spec i.e.

  class Minitest::Spec
    include PDC::Minitest::FixtureExtentions
  end

fails as Minitest modules isn't defined yet. This patch fixes the
failure by defining Minitest module before that.

product-definition-center/pdc-ruby-gem,product-definition-center/pdc-ruby-gem