def on_tag(tag)
      before_scenario do |scenario, step_definitions|
        tags = scenario.tags
        next unless tags.any?
        yield(scenario, step_definitions) if tags.include? tag.to_s
      end
    end
def on_tag(tag)
      before_scenario do |scenario, step_definitions|
        tags = scenario.tags
        next unless tags.any?
        yield(scenario, step_definitions) if tags.include? tag.to_s
      end
    end
Runs before running a scenario with a particular tag

 @param [String] tag
   the tag to match

 @example
   Spinach.hooks.on_tag('javascript') do
     # change capybara driver
   end