Update routes to reflect new image-centric organization.

Since a single pet in the petfinder.com databse can have many
images, it is necessary to place images at the root of our
namespacing and organization.
Update caption controller and associated views.
Use aws helper methods.
Flesh out rmagick meme image creation.
Make rmagick methods private; should only get called by after_save.
Add text_align property to Caption model.
Add text-alignment functionality.
Seperately handle top and bottom text alignment.