Fixes issue with continuedX sometimes not being reset by explicit line break.

[bjnsn]

Fixes issue with calls to text that have continued option not having continuedX reset when an explicit carriage return causes a break.

For example, if you paste this code into the browser demo you'll find that the subsequent lines do not have their position reset to the left edge of the column as expected.

// create a document and pipe to a blob
var doc = new PDFDocument();
var stream = doc.pipe(blobStream());

 doc.font('Times-Roman', 13)
       .text('First, we cause it to wrap onto the next', {
         width: 412,
         columns: 2,
         height: 300,
         continued: true,
         paragraphGap: 10
       });

for (var i = 0; i < 10; ++i) {
    doc.text('\nand then we cause it to wrap onto the next', {continued: i < 9});
}

// end and display the document in the iframe to the right
doc.end();
stream.on('finish', function() {
  iframe.src = stream.toBlobURL('application/pdf');
});