Added FitTransformer and his test

Transformer resizes image to fit given conditions (maxWidth and maxHeight). Resized image will be not larger nor wider.  But one of the dimension may be less than appropriate setting to keep aspect ratio. If `fill` parameter is set as an array(r,g,b), and `verticalAlign` and `horizontalAlign` parameters are set, then ouput image would be exact size as set in `maxWidth` and `maxHeight` and unused bounds of image will be filled by given color.