Changed images to PNG, mofified windows.step to point to new images

Author: mikedao

sites/en/installfest/img/command.jpg

@@ -53,13 +53,13 @@ step "Update Git" do
 
   message "Run the installer, and it will ask you where you want to install it. Change it FROM C:\\Program Files\\Git  TO, C:\\RailsInstaller\\Git like the picture below."
 
-  img src: 'img/directory.jpg'
+  img src: 'img/directory.png'
 
   message "It will warn you that the directory already exists. Click yes to install to that folder anyway."
 
   message "Click next twice, and select, Use Git from the Windows Command Prompt."
 
-  img src: 'img/command.jpg'
+  img src: 'img/command.png'
 
   message "Keep going and you'll have the latest version of Git installed!"