Working proof of concept of spec tag
Centralized spec properies
A little reorganization
Automatically autodiscover
Decorator syntax for registering specs
Use hashes for generated image filenames

While this change means users can no longer specify their own filenames,
changing a property of a processor, for example, will now result in a
new image. This solves a lot of the previous invalidation issues.
Merge branch 'develop' into templatetags

Conflicts:
	imagekit/utils.py
Merge branch 'ik-next' into templatetags
Add VALIDATE_ON_ACCESS setting
Extract useful backend utils
Remove "non-validating" backend

It's been superseded by the VALIDATE_ON_ACCESS setting
Reorganize image cache backends
Add backend for caching image state
Spec templatetag returns html by default

...if no 'as var' is provided or if the var is printed directly.
Include source filename in hash
Add image cache strategies

This new feature gives the user more control over *when* their images
are validated. Image cache backends are now exclusively for controlling
the *how*. This means you won't have to write a lot of code when you
just want to change one or the other.
Remove print statement
Merge branch 'ik-next' into templatetags

Conflicts:
	imagekit/models/fields/__init__.py
	imagekit/utils.py
Merge branch 'tt' into ik-next
Create ImageSpecs; remove generators