data-ignore attribute and added option to add doctype

Not sure if any of this is worthy of adding but, it's helped me. 

I've added code that will allow users to add the **data-ignore** attribute to whatever style tag they apply it to. It works well for media queries. 

I've also noticed that jsdom removes the doctype from the document and certain email clients fuss if there is no doctype present So I went ahead and added an option **addDoctype** which allows the user to enter a string for the doctype.