update phanomjs pdf printing to work with latest pdf css

plugin/print-pdf/print-pdf.js

@@ -11,8 +11,13 @@
 var page = new WebPage();
 var system = require( 'system' );
 
+page.viewportSize  = {
+	width: 1024,
+	height: 768
+};
+
 page.paperSize = {
-	format: 'A4',
+	format: 'letter',
 	orientation: 'landscape',
 	margin: {
 		left: '0',
@@ -21,7 +26,6 @@ page.paperSize = {
 		bottom: '0'
 	}
 };
-page.zoomFactor = 1.5;
 
 var revealFile = system.args[1] || 'index.html?print-pdf';
 var slideFile = system.args[2] || 'slides.pdf';
@@ -37,3 +41,4 @@ page.open( revealFile, function( status ) {
 	page.render( slideFile );
 	phantom.exit();
 } );
+