setAlphaSliderVisible() bug fixed

[mianaliasjad]

I have fixed issue with a scenario:

in XML make app:cpv_alphaChannelVisible="false" and in code on button click colorPickerView.setAlphaSliderVisible(true); it was not showing alpha slider becasue onSizeChanged(int w, int h, int oldw, int oldh) was not gettlng called after requestLayout();

so i have moved code from onSizeChanged(int w, int h, int oldw, int oldh) to onLayout(boolean changed, int left, int top, int right, int bottom). Also created a simple getter method to check if Alpha slider is visible or not.