FIX: The cachebuster now only includes a questionmark, if there is none in the current url...
NEW: Subclasses of Image are now instantiated and used, according to the has_one definition of the corresponding DataObject
NEW: Added a callback before writing the record for the first time, allowing the corresponding DataObject to execute code related to the current gridField.
Merge pull request #14 from s-m/image-subclass

NEW: Subclasses of Image are now instantiated and used
Merge pull request #12 from s-m/cachebuster-fix

FIX: The cachebuster now only includes a questionmark, if there is none in the current url
Merge pull request #13 from s-m/create-callback

NEW: Added a callback before writing the record for the first time