[feature]create photo model
[chore]move like association from image to photos
[feature]move controller from Images to Photos
[chore]clean relation for images and comments
[feature]move photos routes into cards routes
[feature]card's creator can new a photo for the card
[chore]user can create a new photo for a card
[test]add tests for photos_controller#create
[feature]create photos for public/private cards
Merge pull request #18 from peterzd/create_image

Create image