Make CarrierWave::MiniMagick#mini_magic_image private

This method doesn't need to be part of the public API. It's used by
the new public `#width` and `#height` methods (introduced by carrierwaveuploader#1405).

This commit also fixes a typo in the method name and tweaks the comments.

lib/carrierwave/processing/mini_magick.rb

@@ -245,40 +245,25 @@ def resize_and_pad(width, height, background=:transparent, gravity='Center', com
     end
 
     ##
-    # Return the mini magic instance of the image
-    #
-    # === Returns
-    #
-    # #<MiniMagick::Image>
-    #
-    def mini_magic_image
-      if url
-        ::MiniMagick::Image.open(url)
-      else
-        ::MiniMagick::Image.open(current_path)
-      end
-    end
-
-    ##
-    # Gives the width of the image, useful for model validation
+    # Returns the width of the image in pixels.
     #
     # === Returns
     #
     # [Integer] the image's width in pixels
     #
     def width
-      mini_magic_image[:width]
+      mini_magick_image[:width]
     end
 
     ##
-    # Gives the height of the image, useful for model validation
+    # Returns the height of the image in pixels.
     #
     # === Returns
     #
     # [Integer] the image's height in pixels
     #
     def height
-      mini_magic_image[:height]
+      mini_magick_image[:height]
     end
 
     ##
@@ -338,5 +323,15 @@ def append_combine_options(cmd, combine_options)
       end
     end
 
+    private
+
+      def mini_magick_image
+        if url
+          ::MiniMagick::Image.open(url)
+        else
+          ::MiniMagick::Image.open(current_path)
+        end
+      end
+
   end # MiniMagick
 end # CarrierWave

spec/processing/mini_magick_spec.rb

@@ -156,6 +156,14 @@
     end
   end
 
+  describe "#width and #height" do
+    it "should return the width and height of the image" do
+      @instance.resize_to_fill(200, 300)
+      expect(@instance.width).to eq(200)
+      expect(@instance.height).to eq(300)
+    end
+  end
+
   describe "test errors" do
     context "invalid image file" do
       before do
@@ -188,12 +196,4 @@
     end
   end
 
-  describe "return_width_and_height" do
-    it "should return the width and height of the image" do
-      @instance.resize_to_fill(200, 300)
-      expect(@instance.width).to eq(200)
-      expect(@instance.height).to eq(300)
-    end
-  end
-
 end