Rename metadata into metadata_backend
Merge pull request #35 from SeiryuZ/metadata-backend

Rename metadata into metadata_backend
Merge pull request #40 from SeiryuZ/master

Raise value error on non-existant source image
Gallery object should now raise ValueError if user tries to create
a thumbnail from an empty image field.
Merge branch 'master' into fix-error-not-surpressed

Conflicts:
	thumbnails/files.py