upload image form has been styled, added validations to image model so that user_id and url must be present to submit image for saving to the database.
Merge branch 'master' of github.com:zhbanton/photo_mixer
Users have both a :small_avatar and :large_avatar
made corrections to image model validations (image_path, not url, must be present).

My images view is now styled.
Merge branch 'master' of github.com:zhbanton/photo_mixer into avatars_of_many_sizes