Possible to remove dependency of `activesupport`?

[PikachuEXE]

The only place that is using it is https://github.com/DarthSim/carrierwave-bombshelter/blob/master/lib/carrierwave/bombshelter.rb#L14

But it can be replaced easily with

def self.included(base)
  base.class_eval do # or `module_eval`
      # `before` puts callback in the end of queue, but we need to run this
      # callback first.
      # before :cache, :protect_from_image_bomb!
      self._before_callbacks = _before_callbacks.merge(
        cache: [:protect_from_image_bomb!] + _before_callbacks[:cache]
      )
  end
end

[DarthSim]

Hi. Make a PR please.

[PikachuEXE]

Opened as #19