add mini_magick gem
generate user_pictue_uploader.rb, configure default_normal and thumb picture versions, add default user pic to assets/images
update .gitignore
add_picture_to_users migration
mount uploader to user model, add picture to registrations_controller params
add picture file_field to form in registrations new and edit views
display normal pic in user/show, display thumb pic for create_by: in tutorials/show