Create super sweet image model
Update gemfile

Adds mini_magick to it, for image processing
Save image after saving associated model
Set a width and height of images as they’re saved

We’ll want that to make page layouts happen fast.
Switch to 1x1 pixel gif for our fixture

This makes test output and logging a lot less dumb
Allow images up to 16MB in size
Display thumbnails of avatars on the edit form