removes img url input field from create listing form
removes img attribute from listing
create listing form now redirects to add photos view
create listing form is now a multipart form that users can add images to. These images are uploaded to S3
add photos usecase now generates a thumbnail using the image passed in by the user
add photo use case now generates a preview size and hero size images
hero file size is 500 by 375
specifies datatype in users ajax request
creates a buffer for rmagick objects
Merge branch 'development' of https://github.com/felguerez/aircycle into create_listing_form

Conflicts:
	lib/air_cycle/entities/listing.rb
	spec/db/shared_spec.rb
	web/app/controllers/listings_controller.rb
	web/app/views/listings/index.html.erb
	web/app/views/listings/new.html.erb
Merge pull request #83 from felguerez/create_listing_form

Create listing form