Use cursive font-family if SignatureFont cannot be loaded

There was an issue on iOS when SignatureFont was not loaded that question marks would be generated. This will use the OS's generic cursive font until SignatureFont can be loaded.

Author: David Khuu

injectedJavaScript/application.js

@@ -71,7 +71,7 @@ var content = (penColor, backgroundColor, dataURL, penMinWidth, penMaxWidth, use
     var textHeight = 18;
     var textWidth = -1;
     do {
-      context.font = fontSize + "px SignatureFont";
+      context.font = fontSize + "px SignatureFont, cursive";
       textWidth = context.measureText("${name}").width;
       fontSize = 7 * fontSize / 8;
     } while (textWidth + (w * 0.05) > w);