Add paperclip images to products

Squashed commit of the following:

commit a6f915ad14d6cec185467ca1ff9ccbac2538a8d2
Author: Everton J. Carpes <everton.carpes@gmail.com>
Date:   Mon Feb 18 05:39:27 2013 -0300

    Add images for product with upload on admin

commit dfd3996b31f9167dde6e6fdd84dad8755bd325e8
Author: Everton J. Carpes <everton.carpes@gmail.com>
Date:   Mon Feb 18 05:38:50 2013 -0300

    Add migration for image on products

commit 8d70c75a584d9e8fad4d70789381cd169c47031b
Author: Everton J. Carpes <everton.carpes@gmail.com>
Date:   Mon Feb 18 04:35:13 2013 -0300

    Add paperclip gem