Fix to keep options when creating new Cheerio instances

Before Cheerio instances would not keep options (and send these to the
html parser). This would lead to xmlMode being set to false when
creating new dom nodes in a Cheerio instance instantiated with xmlMode:
true.

This fix simply overwrites the default Cheerio.prototype.options with
given options when present. And sends these options to the parser when
creating new dom nodes

E.g newNode will keep options from $ in this case: $ =
cheerio.load('<svg></svg>', { xmlMode: true }), newNode = $('<g
someCamelcasedAttribute="something"></g>);
So that newNode is not .toLowerCase'd in htmlparser2.