Update console script help message with default file format

Author: maribedran

qrcode/console_scripts.py

@@ -3,7 +3,8 @@
 qr - Convert stdin (or the first argument) to a QR Code.
 
 When stdout is a tty the QR Code is printed to the terminal and when stdout is
-a pipe to a file an image is written. The default image format is PNG.
+a pipe to a file an image is written. The default image format is PNG if pil or
+png optional dependencies are installed, otherwise SVG.
 """
 
 import optparse