Add option setWidth to prevent width being set on "stickied" element

At the moment, a fixed width is set on the "sticky" element. For my use case, this isn't necessary since the CSS continues to set the width correctly when "sticked".

However, the fixed width causes the layout to break when the page is resized since the width isn't recalculated. Adding an option to prevent the width being set sorts out the problem for me.