Avoid extra blank page (with A4, in some unexpected cases)

The A4 paper size has been defined with more precision, in order to
avoid an extra blank page in cases such as this one :

self.PDFCreator = [NDHTMLtoPDF createPDFWithHTML:@"Hello"
pathForPDF:[@"~/Documents/demo.pdf" stringByExpandingTildeInPath]
delegate:self pageSize:kPaperSizeA4 margins:UIEdgeInsetsMake(36, 36,
36, 36)];
Merge pull request #10 from fblondiau/master

Avoid extra blank page (with A4, in some unexpected cases)