public void setPresetTransformer(String transformerName){
        for(Transformer t : Transformer.values()){
            if(t.equals(transformerName)){
                setPresetTransformer(t);
                return;
            }
        }
    }
set preset PagerTransformer via the name of transforemer.
@param transformerName
library/src/main/java/com/daimajia/slider/library/SliderLayout.java