title: Undefined method manipulate! - carrierwave with minimagick
body: <p>I am using carrierwave with minimagick to upload an image and crop it to a square. However I get the following error:</p>
  
  <pre><code>undefined method 'manipulate!' for #&lt;Class:0x692db10&gt;
  </code></pre>
  
  <p>it seems to make no sense, as i have included the correct class, and that part works fine. Heres my current uploader class.</p>
  
  <pre><code>class ImageUploader &lt; CarrierWave::Uploader::Base
  
    include CarrierWave::MiniMagick
  
    @@sizes = {
      "2000" =&gt; 2048,
      "1500" =&gt; 1500,
      "1000" =&gt; 1024,
      "500" =&gt; 512,
      "250" =&gt; 256,
      "100" =&gt; 128
    }
  
    storage :file
  
    def store_dir
      "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
    end
  
    version :square do
      manipulate! do |img|
        size = img.dimensions.min
      end
      process resize_to_fill: [size, size]
    end
  end
  </code></pre>
  
  <p>to be clear, we are talking about the <code>:square</code> version. Does anyone have any idea what could be wrong?</p>