Add CRUD for photos
Move cassettes to fixtures directory

We are going to keep our test subjects in one directory.
Fix docs in delete methods
Remove filename when creating photos

It's not mandatory anymore, it will be lost during image processing anyway.
It's possible to upload a photo as file path, encoded photo or remote photo url
Rename cancel rental to delete rental
Merge pull request #40 from BookingSync/photos-crud

Full photos CRUD